Help!!! My cooling fan issue is driving me insane! (long)
06-22-2004, 11:28 PM
#1
Burning Brakes
Thread Starter
Help!!! My cooling fan issue is driving me insane! (long)
Here is the situation: I purchased my '87 S4 last October and inherited a cooling fan issue. Basically, the drivers side fan is non operable. As a result, the passenger side cooling fan picks up the slack. But, due to the wonder of German engineering, the brains behind the cooling fan operations feels that the one working fan needs to work overtime in order to compensate. As a result, the fan kicks on at full speed for about 15 seconds, off for about 5 seconds, and then kicks back on again. In addition, whenever the fan kicks on the cooling flaps open up to increase the airflow. This happens when stopped and also at speed. My coolant level gauge always hovers at the second lowest bar, so at least I know that the fan and the flaps are doing their job.
This doesn't affect the operation of the car, but I am concerned long term about the fan...if it is always on, it will wear a lot faster. And, the thing is just really damn loud...it sucks to be stopped in the light and have the pleasant burble of the V8 and the RMB overshadowed by this raging fan noise going on and off!
So here is what I have done.
1) Checked fuses and relays - all are good.
2) Checked the fan - it spins smoothly, so i think the bearings are in good shape. I hooked up my other car directly to the fan and it started spinning, so I know that the fan itself can receive power.
3) Replaced the fan unit in the engine bay - the black unit with the fins on the front passenger side of the engine in front of the fan. The old one looked ok, but they are prone to fail. This didn't change a thing.
4) Replaced the cooling fan unit inside the passenger compartment - the silver rectangular computer between the passenger seat and the door sill. This also did not do anything.
(both of the above pieces are from 928 Intl., so I know they work)
5) I have also checked the wiring to the extent of my abilities. The wiring into the back of the fuse panel looks fine - no cracks or broken wires. The wiring into the fans themselves look to be in fine shape, but I have not taken them off completely to inspect. I have used my power meter to verifiy that there is connectivity to the fan itself, but it is very hard to test this completely because the fan itself only receives a current when the fan computer tells it to turn on. With spinning fans and belts, I have not been able to tell if it is receiving current.
The funny thing is, when I was doing all of this testing one day, I actually got the damn fan to work. Unfortunately, I don't know what might have done it since I was messing with so much
and it only lasted for a short while before it stopped working again.
The only thing I can think of is it is either a bad switch on the fan itself, or there is a break somewhere in the wiring. Unfortunately, the wiring looks to go from the fans themselves all the way back to the fuse panel, as well as from the fan control units to the fuse panel. Very confusing, and I don't know if I can get at all the wiring without pulling some major components from the engine bay.
Any ideas? I am pulling my hair out trying to figure this out...all of the possible solutions on Rennlist and elsewhere have not helped. Please, please help!
I would be eternally in your debt, and would be beholden to purchasing many beverages to my savior at the next 928 event I find them at!
Bill
This doesn't affect the operation of the car, but I am concerned long term about the fan...if it is always on, it will wear a lot faster. And, the thing is just really damn loud...it sucks to be stopped in the light and have the pleasant burble of the V8 and the RMB overshadowed by this raging fan noise going on and off!
So here is what I have done.
1) Checked fuses and relays - all are good.
2) Checked the fan - it spins smoothly, so i think the bearings are in good shape. I hooked up my other car directly to the fan and it started spinning, so I know that the fan itself can receive power.
3) Replaced the fan unit in the engine bay - the black unit with the fins on the front passenger side of the engine in front of the fan. The old one looked ok, but they are prone to fail. This didn't change a thing.
4) Replaced the cooling fan unit inside the passenger compartment - the silver rectangular computer between the passenger seat and the door sill. This also did not do anything.
(both of the above pieces are from 928 Intl., so I know they work)
5) I have also checked the wiring to the extent of my abilities. The wiring into the back of the fuse panel looks fine - no cracks or broken wires. The wiring into the fans themselves look to be in fine shape, but I have not taken them off completely to inspect. I have used my power meter to verifiy that there is connectivity to the fan itself, but it is very hard to test this completely because the fan itself only receives a current when the fan computer tells it to turn on. With spinning fans and belts, I have not been able to tell if it is receiving current.
The funny thing is, when I was doing all of this testing one day, I actually got the damn fan to work. Unfortunately, I don't know what might have done it since I was messing with so much
and it only lasted for a short while before it stopped working again.The only thing I can think of is it is either a bad switch on the fan itself, or there is a break somewhere in the wiring. Unfortunately, the wiring looks to go from the fans themselves all the way back to the fuse panel, as well as from the fan control units to the fuse panel. Very confusing, and I don't know if I can get at all the wiring without pulling some major components from the engine bay.
Any ideas? I am pulling my hair out trying to figure this out...all of the possible solutions on Rennlist and elsewhere have not helped. Please, please help!
I would be eternally in your debt, and would be beholden to purchasing many beverages to my savior at the next 928 event I find them at! Bill
06-22-2004, 11:46 PM
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Hey Bill,
The first step is to plug the right side connector into the left side fan and see if it works. (You'll have to either use an extender or pull the fans and change the connections with the fans on the ground and the harness pulled down). If it does you may have a bad left side wire or a problem with the Final Output Stage. That's the black, finned, flat box on the passenger's side of your car in front of the AC condenser.
From the sound of your description I'd bet on a bad wire or connection to the fan.
The first step is to plug the right side connector into the left side fan and see if it works. (You'll have to either use an extender or pull the fans and change the connections with the fans on the ground and the harness pulled down). If it does you may have a bad left side wire or a problem with the Final Output Stage. That's the black, finned, flat box on the passenger's side of your car in front of the AC condenser.
From the sound of your description I'd bet on a bad wire or connection to the fan.
06-23-2004, 12:28 AM
#3
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The module that fits to the right of the passenger seat is the controller for the cooling flaps. If you live in a warmer climate where there really isn't a need for the cooling flaps, just pull fuse 23 when the engine is off. This keeps the flaps open all the time.
It is VERY important that both fans run. One problem that can happen with only one fan running is the A/C high pressure can become too high and parts can blow out!
It is VERY important that both fans run. One problem that can happen with only one fan running is the A/C high pressure can become too high and parts can blow out!
06-23-2004, 04:22 AM
#4
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Bill
As Ernest says it is probably an intermittent connection somewhere.
Pull the connection to the "bad" fan then with the Engine running and hot use a voltmeter across the fan connector to check if volts are getting to the connector when the other fan is running. It may be worthwhile making some test leads with the correct spade terminals on to get a robust connection to the fan connector. This will allow you to wiggle the fan wiring around to see if this causes an intermittent break.
However my best guess is that the connection between the male spade connectors on the fan motor body and the internal wiring of the fan motor is where the intermittent fault is. The connector module on the fan motor (Not the one on the end of the wiring loom) looks like it will unlatch from the motor body. It wont. You need to take the fan out and dissasemble the motor to check these connections.
Regards
Jon
Black SE
Silver 91 GT
As Ernest says it is probably an intermittent connection somewhere.
Pull the connection to the "bad" fan then with the Engine running and hot use a voltmeter across the fan connector to check if volts are getting to the connector when the other fan is running. It may be worthwhile making some test leads with the correct spade terminals on to get a robust connection to the fan connector. This will allow you to wiggle the fan wiring around to see if this causes an intermittent break.
However my best guess is that the connection between the male spade connectors on the fan motor body and the internal wiring of the fan motor is where the intermittent fault is. The connector module on the fan motor (Not the one on the end of the wiring loom) looks like it will unlatch from the motor body. It wont. You need to take the fan out and dissasemble the motor to check these connections.
Regards
Jon
Black SE
Silver 91 GT
06-23-2004, 09:31 AM
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bill,
if you want to take a ride down to fredericksburg, i have an extra set of fans as well as both control boxes and the wiring harness. we could switch some parts to troubleshoot and maybe find the culprit.
if you want to take a ride down to fredericksburg, i have an extra set of fans as well as both control boxes and the wiring harness. we could switch some parts to troubleshoot and maybe find the culprit.
06-23-2004, 11:39 AM
#6
Chronic Tool Dropper
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A lister in SoCal was suffering the same problem. Here's what they did. First, they tried swapping modules. Next, did all the meter diagnostics described on the FSM. Still no go. Swapped connections, problem stayed the same. Then the car was brough over for some more advanced diagnostics.
Drum roll please--
The fan circuits are considered "essential" by Porsche engineers, and therefore have their own dedicated, individual wires and connections directly from the battery to the fuse panel. Each fan has its own wire directly from the battery, through its own dedicated fuse in the panel, to the fan module on the front apron. So before you go any further, open the spare tire well and get the battery box cover open. Look at the positive terminal on the battery, and notice that there are two large red cables connected to the bolt on the terminal clamp, in addition to the main cable that runs directly into the clamp.
After lifting and isolating the body ground strap at the rear apron, remove the positive clamp completely from the battery post, and remove those two red connections from the bolt. Using a wire brush, clean the cable clamp completely until it is shiny. Clean the post on the battery the same way. On the clamp, make sure the area at the bolt is also completely cleaned so it is shiny. On the eyelet terminals attached to the two red cables, verify that the insulation is intact and ther there is no corrosion working its way up inside the insulation. Using that wire brush and some fine sandpaper, clean the eyelet terminals so they are shiny, and reattach them to the clamp and the clamp to the battery. Do the same clean until shiny treatment to the negative terminal on the battery and the frame end of the ground strap while you are in there. After you have verified operation, coat all the connections with a thin film of Vaseline to keep the corrosive battery fumes from destroying all your handiwork.
To test the fan (S4 and later cars...), you can open the hood and pull the two wires that connect to the thermo switch at the top of the intake manifold. Connect those two wires together, and the fan should run after a few seconds. Note that you may have to secure the hood safety switch (on the passenger side of the engine bay) to fool the system into thinking the hood is closed.
Theo Jenkison's Tech Tips page at http://home.wxs.nl/~Jennit/Technical/Tips/TechTips.htm has a detailed procedure for DIY replacement of the FET elements in the front controller, if that turns out to be an issue for you. It sounds like you have swapped this and eliminated it as a possibility. The temp controller next to the passenger seat sounds like it's doing its job just fine, operating the fan module and the flaps just like the manual suggests it will when there's a fan problem.
When the local guy came over for some fan diagnostics, it took over an hour of careful examination of the car and the wiring diagrams in the manuals to figure out where the problem was. We traced control and sensor wiring back through the hood switch, the radio bucket where the hood switch wiring parallels the alarm wire there, and had the connectors to the pass side temp control module completely apart to chase every connection down. We had the fuse panel laying out on the floor upside-down to get to the wiring at the rear and prove every connection to the fans was sound. In the end, it was the cable connections at the battery, the last thing you check as you work your way from the fans back to the power source.
With any luck, you can learn vicariously from our lesson, and quickly find that you have the same problem and the easy solution. These battery connections are often missed even when folks do their annual battery box service. A little bit of corrosion there is all it takes to keep the fans from running well. Plus it's tough to diagnose with a meter, because the terminal may easily flow enough current to get the meter to read full voltage. It's only when the load of the fans is on there that the voltage drops enough to see it on the meter.
Anyway, hope this helps! Please let us know what you find.
Drum roll please--
The fan circuits are considered "essential" by Porsche engineers, and therefore have their own dedicated, individual wires and connections directly from the battery to the fuse panel. Each fan has its own wire directly from the battery, through its own dedicated fuse in the panel, to the fan module on the front apron. So before you go any further, open the spare tire well and get the battery box cover open. Look at the positive terminal on the battery, and notice that there are two large red cables connected to the bolt on the terminal clamp, in addition to the main cable that runs directly into the clamp.
After lifting and isolating the body ground strap at the rear apron, remove the positive clamp completely from the battery post, and remove those two red connections from the bolt. Using a wire brush, clean the cable clamp completely until it is shiny. Clean the post on the battery the same way. On the clamp, make sure the area at the bolt is also completely cleaned so it is shiny. On the eyelet terminals attached to the two red cables, verify that the insulation is intact and ther there is no corrosion working its way up inside the insulation. Using that wire brush and some fine sandpaper, clean the eyelet terminals so they are shiny, and reattach them to the clamp and the clamp to the battery. Do the same clean until shiny treatment to the negative terminal on the battery and the frame end of the ground strap while you are in there. After you have verified operation, coat all the connections with a thin film of Vaseline to keep the corrosive battery fumes from destroying all your handiwork.
To test the fan (S4 and later cars...), you can open the hood and pull the two wires that connect to the thermo switch at the top of the intake manifold. Connect those two wires together, and the fan should run after a few seconds. Note that you may have to secure the hood safety switch (on the passenger side of the engine bay) to fool the system into thinking the hood is closed.
Theo Jenkison's Tech Tips page at http://home.wxs.nl/~Jennit/Technical/Tips/TechTips.htm has a detailed procedure for DIY replacement of the FET elements in the front controller, if that turns out to be an issue for you. It sounds like you have swapped this and eliminated it as a possibility. The temp controller next to the passenger seat sounds like it's doing its job just fine, operating the fan module and the flaps just like the manual suggests it will when there's a fan problem.
When the local guy came over for some fan diagnostics, it took over an hour of careful examination of the car and the wiring diagrams in the manuals to figure out where the problem was. We traced control and sensor wiring back through the hood switch, the radio bucket where the hood switch wiring parallels the alarm wire there, and had the connectors to the pass side temp control module completely apart to chase every connection down. We had the fuse panel laying out on the floor upside-down to get to the wiring at the rear and prove every connection to the fans was sound. In the end, it was the cable connections at the battery, the last thing you check as you work your way from the fans back to the power source.
With any luck, you can learn vicariously from our lesson, and quickly find that you have the same problem and the easy solution. These battery connections are often missed even when folks do their annual battery box service. A little bit of corrosion there is all it takes to keep the fans from running well. Plus it's tough to diagnose with a meter, because the terminal may easily flow enough current to get the meter to read full voltage. It's only when the load of the fans is on there that the voltage drops enough to see it on the meter.
Anyway, hope this helps! Please let us know what you find.
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06-23-2004, 01:02 PM
#8
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The control unit (I'm not sure if it's the FOS or the silver controller) is sensing a fault, that's why you're getting the on/off full speed control.
Here's what I would do:
1. Check all electrical connections (make sure you check the battery terminal per Dr. Bob's post).
2. Make sure you can get both fans to work by directly putting battery power to each. This will make them spin at full rpm.
3. If all is well, there is a really good FSM troubleshooting guide that will point out what part (of this overly complex) cooling system is bad. Make sure you use the right troubleshooting guide as the original one found in the FSM was revised. PM me if you need the revised one.
I chased a similar problem for some time. I was almost ready to give up when I noticed one of the solder joints in the silver control box was loose. I soldered it up and everything works properly.
Good Luck, you will find it.
Here's what I would do:
1. Check all electrical connections (make sure you check the battery terminal per Dr. Bob's post).
2. Make sure you can get both fans to work by directly putting battery power to each. This will make them spin at full rpm.
3. If all is well, there is a really good FSM troubleshooting guide that will point out what part (of this overly complex) cooling system is bad. Make sure you use the right troubleshooting guide as the original one found in the FSM was revised. PM me if you need the revised one.
I chased a similar problem for some time. I was almost ready to give up when I noticed one of the solder joints in the silver control box was loose. I soldered it up and everything works properly.
Good Luck, you will find it.
06-23-2004, 09:48 PM
#9
Burning Brakes
Thread Starter
The generosity of 928 owners never ceases to amaze me. This is why I am keeping this car (and the others I will eventually acquire) for the rest of my life! 
928 owners are definitely a cut above the rest...
Dr. Bob, I will give your suggestion a whirl and update you all on my success.
Tom, if I am unable to solve it this weekend I will come to Fredricksburg whenever you are free (heck, I would come down just to shoot the breeze and look at all your toys!)
Thanks again everyone!
Bill
928 owners are definitely a cut above the rest...Dr. Bob, I will give your suggestion a whirl and update you all on my success.
Tom, if I am unable to solve it this weekend I will come to Fredricksburg whenever you are free (heck, I would come down just to shoot the breeze and look at all your toys!)
Thanks again everyone!
Bill
06-28-2004, 07:30 PM
#10
Burning Brakes
Thread Starter
*Updated*Help!!! My cooling fan issue is driving me insane! (long)
Well, unfortunately, still no luck with the fans. I followed Dr. Bob's battery cleanup directions to the letter, with no change in the fan operation. Then I swapped the connectors into the fans, and got the left fan to operate with the right connector - checked the left connector and I am getting no current flowing. So, to summarize:
Fans - working correctly
Front fan control unit(engine) - repplaced - working correctly
Temp control unit(passenger compartment) replaced - working correctly
Fuses - checked, working correctly
Battery connections - clean and shiny
So, it would seem it would HAVE to be somewhere in the wiring, right? I have gone the whole range of emotions on this one, from annoyance, to frustration, to anger, to rage, and have now transcended to purely intrigued as to the complexity of this system and how to find a solution...I don't know what that says about me though
Anyway, I guess the next step is to start pulling the wire and looking for breaks? The engine side of the wiring harness for the cooling system is pretty embedded into the fender as it starts back to the firewall...is this a major operation or is it doable without pulling large parts of the engine? Should I get another wiring harness to be safe?
Thanks again for all of the help...
Bill
PS, Aaron, I PM'd you for the revised FSM guide. Thanks!
Fans - working correctly
Front fan control unit(engine) - repplaced - working correctly
Temp control unit(passenger compartment) replaced - working correctly
Fuses - checked, working correctly
Battery connections - clean and shiny
So, it would seem it would HAVE to be somewhere in the wiring, right? I have gone the whole range of emotions on this one, from annoyance, to frustration, to anger, to rage, and have now transcended to purely intrigued as to the complexity of this system and how to find a solution...I don't know what that says about me though
Anyway, I guess the next step is to start pulling the wire and looking for breaks? The engine side of the wiring harness for the cooling system is pretty embedded into the fender as it starts back to the firewall...is this a major operation or is it doable without pulling large parts of the engine? Should I get another wiring harness to be safe?
Thanks again for all of the help...
Bill
PS, Aaron, I PM'd you for the revised FSM guide. Thanks!
06-28-2004, 08:29 PM
#11
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One suggestion, the wires to the fans have to be removed and put out of the way for a whole bunch of procedures, the metal clips that hold the wires into the fan shroud are sharp.
Pull the wires off the fans and the shroud, check the wires visually, also check where the wires bend at 90degrees around the radiator.
If there was going to be a failure in the wires and with your check list above this is where I would look next before you dig deeper.
Chris
Pull the wires off the fans and the shroud, check the wires visually, also check where the wires bend at 90degrees around the radiator.
If there was going to be a failure in the wires and with your check list above this is where I would look next before you dig deeper.
Chris
06-28-2004, 09:06 PM
#12
Chronic Tool Dropper
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OK--
1) Verify that there is voltage on one side of each fan fuse (28 & 29 IIRC...), test in the fuse panel with each fuse removed. If there is voltage on one side of each fuse, continue to step 3.
2) If there is no voltage on one of the fuse holder connections, you are chasing a problem betwen the fuse panel and the battery. One of those wires is disconnected or broken.
3) With voltage available on one side of each fuse, continue with your test light/meter to verify that each fuse is good. Use the OHMS function to see that there is less than 2 ohms resistance through each fuse as you hold it in your hand. If resistance is higher or infinite, replace the fuse with new.
4) Inspect the fuse panel sockets for these fuses to see if there's any sign of melting or charring of the plastic that might indicate a bad connection there. If all is OK, replace the fuses and proceed to the controller at the front engine bay apron.
5) The wiring diagrams in the FSM shows that voltage from the fuse should show up at pins 1 and 4 of the connector at that box, referred to in the diagram as the 'cooling fan amplifier'. Check for battery voltage at these conections by removing the connector from the module and using the voltmeter function, referenced to ground. If you don't have voltage at both connector pins, you have a problem between the fuse panel and the module. If you have voltage, your fans should run.
6) Assuming you don't have voltage, you are looking for a broken wire or bad connection in the harness or at the fuse panel. You can use a 'fox 'n' hounds' style circuit chaser, or start at the fuse panel end and see what's damaged.
Disconnect and isolate the battery ground at the rear apron under the tool panel so there's no power to the fuse panel or anything else.
Unbolt the fuse panel and -carefully- roll it so you can see the back of the panel at fuses 28 and 29. Any signs of meltdown, corrosion, or broken wire? Look for red from the battery end, and red/WS (white stripe) from the fuse panel to the module.
You can test the wiring between the fuse panel and the module using your ohmmeter again. First install a jumper from wiring harness plug connection 1 to ground at the module end. Test both wires for resistance to ground at the fuse panel end using the ohm meter. One of the two should show very low resistance to ground. If there are more than a few ohms, the problem is probably that conductor. Test the other lead the same way by grounding connection 4 at the module end, and use your ohm meter again to test for continuity to ground at the fuse-panel end of both wires. Again, one should show very low resistance.
From the connector at the module you can verify that a wiring problem does not exist between thr module and the fans. Lift the connector from the module, and use your ohmmeter to measure from wiring harness connector pins 5 and 8 to ground. Resistance should be low, on the order of probably 10 ohms or less, if the wiring is intact. This test is done with both fans plugged in. If one has high resistance, the problem is in the wiring between the module connector and the wiring connector where the fan plugs in.
Let me know what you find after each of the above tests and we can get into this deeper.
1) Verify that there is voltage on one side of each fan fuse (28 & 29 IIRC...), test in the fuse panel with each fuse removed. If there is voltage on one side of each fuse, continue to step 3.
2) If there is no voltage on one of the fuse holder connections, you are chasing a problem betwen the fuse panel and the battery. One of those wires is disconnected or broken.
3) With voltage available on one side of each fuse, continue with your test light/meter to verify that each fuse is good. Use the OHMS function to see that there is less than 2 ohms resistance through each fuse as you hold it in your hand. If resistance is higher or infinite, replace the fuse with new.
4) Inspect the fuse panel sockets for these fuses to see if there's any sign of melting or charring of the plastic that might indicate a bad connection there. If all is OK, replace the fuses and proceed to the controller at the front engine bay apron.
5) The wiring diagrams in the FSM shows that voltage from the fuse should show up at pins 1 and 4 of the connector at that box, referred to in the diagram as the 'cooling fan amplifier'. Check for battery voltage at these conections by removing the connector from the module and using the voltmeter function, referenced to ground. If you don't have voltage at both connector pins, you have a problem between the fuse panel and the module. If you have voltage, your fans should run.
6) Assuming you don't have voltage, you are looking for a broken wire or bad connection in the harness or at the fuse panel. You can use a 'fox 'n' hounds' style circuit chaser, or start at the fuse panel end and see what's damaged.
Disconnect and isolate the battery ground at the rear apron under the tool panel so there's no power to the fuse panel or anything else.
Unbolt the fuse panel and -carefully- roll it so you can see the back of the panel at fuses 28 and 29. Any signs of meltdown, corrosion, or broken wire? Look for red from the battery end, and red/WS (white stripe) from the fuse panel to the module.
You can test the wiring between the fuse panel and the module using your ohmmeter again. First install a jumper from wiring harness plug connection 1 to ground at the module end. Test both wires for resistance to ground at the fuse panel end using the ohm meter. One of the two should show very low resistance to ground. If there are more than a few ohms, the problem is probably that conductor. Test the other lead the same way by grounding connection 4 at the module end, and use your ohm meter again to test for continuity to ground at the fuse-panel end of both wires. Again, one should show very low resistance.
From the connector at the module you can verify that a wiring problem does not exist between thr module and the fans. Lift the connector from the module, and use your ohmmeter to measure from wiring harness connector pins 5 and 8 to ground. Resistance should be low, on the order of probably 10 ohms or less, if the wiring is intact. This test is done with both fans plugged in. If one has high resistance, the problem is in the wiring between the module connector and the wiring connector where the fan plugs in.
Let me know what you find after each of the above tests and we can get into this deeper.
07-06-2004, 09:52 PM
#13
Burning Brakes
Thread Starter
Sorry for the delay - took the shark on a little holiday trip
So, Dr. Bob, I ran through all of the tests you indicated.
1 - Voltage at fuses - both are reading 12.3 Volts
2 - Because #1 checks out, power from battery to fuse panel is good
3 - Fuses check out - even swapped 28 and 29 - left fan refuses to run
4 - Fuse panel looks spotless - both back and front
5 - Bridged the thermostat to force the fans on - pins 1 and 4 on the amplifier check out with 12.3 volts
6 - Since 5 checks out, assume connection between panel and amplifier is in good shape.
That leaves the wiring between the fan itself and the fuse panel. I have checked the connectors to the fan themselves, and the inoperable fan is getting no power from the connector; the working (right) fan is getting 12.3 volts.
So, prior to pulling the wires, I check the ohms on pins 5 and 8 of the amplifier connector - both read the same, about 2 ohms, which implies that there is a working circuit to each fan. Which confuses the hell out of me because how could there be a connection to the inoperable fan if I get no voltage at the connector to the fan? Just to be on the safe side, i prop close the hood switch to simulate the hood being closed. Pins 5 and 8 still read the same number of ohms. But, get this...I plug the connector back into the amplifier, and as usual, the right fan starts working overtime as usual. But as I go to turn the ignition off, the note of the fan changes - i look back at the fans - BOTH OF THE FANS ARE WORKING!!!
(*&%(&^)*&^_(*&#$_*)&#$%_(*&#$%_+)*&($%_+)&*($#_+)*(%
What the F-ING F)*&)(& is going on? How could testing the connections, all of which appear to work, get the fan working? The only connection i was really working with was the connector to the fan amplifier, and this is a new used amplifier from 928 international, so I know it works! Could it be the connector itself? Or could it have something to do with the hood switch? I don't see how it could, but I am a novice at this...
I am sorry for all of the trouble, but I don't know if even a expert 928 mechanic could figure this one out...at least, not without a blank check from me :-)
I love my car, but can't stand it sometimes - just like a woman!
Anyway, Dr. Bob, sorry to bug you, but if you or anyone else has any advice, I would appreciate it...although at this point I think I need an excorcism! Too bad I'm not Catholic...
So, Dr. Bob, I ran through all of the tests you indicated.
1 - Voltage at fuses - both are reading 12.3 Volts
2 - Because #1 checks out, power from battery to fuse panel is good
3 - Fuses check out - even swapped 28 and 29 - left fan refuses to run
4 - Fuse panel looks spotless - both back and front
5 - Bridged the thermostat to force the fans on - pins 1 and 4 on the amplifier check out with 12.3 volts
6 - Since 5 checks out, assume connection between panel and amplifier is in good shape.
That leaves the wiring between the fan itself and the fuse panel. I have checked the connectors to the fan themselves, and the inoperable fan is getting no power from the connector; the working (right) fan is getting 12.3 volts.
So, prior to pulling the wires, I check the ohms on pins 5 and 8 of the amplifier connector - both read the same, about 2 ohms, which implies that there is a working circuit to each fan. Which confuses the hell out of me because how could there be a connection to the inoperable fan if I get no voltage at the connector to the fan? Just to be on the safe side, i prop close the hood switch to simulate the hood being closed. Pins 5 and 8 still read the same number of ohms. But, get this...I plug the connector back into the amplifier, and as usual, the right fan starts working overtime as usual. But as I go to turn the ignition off, the note of the fan changes - i look back at the fans - BOTH OF THE FANS ARE WORKING!!!
(*&%(&^)*&^_(*&#$_*)&#$%_(*&#$%_+)*&($%_+)&*($#_+)*(%
What the F-ING F)*&)(& is going on? How could testing the connections, all of which appear to work, get the fan working? The only connection i was really working with was the connector to the fan amplifier, and this is a new used amplifier from 928 international, so I know it works! Could it be the connector itself? Or could it have something to do with the hood switch? I don't see how it could, but I am a novice at this...
I am sorry for all of the trouble, but I don't know if even a expert 928 mechanic could figure this one out...at least, not without a blank check from me :-)
I love my car, but can't stand it sometimes - just like a woman!
Anyway, Dr. Bob, sorry to bug you, but if you or anyone else has any advice, I would appreciate it...although at this point I think I need an excorcism! Too bad I'm not Catholic...
07-06-2004, 10:40 PM
#14
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Do you have a copy of the workshop manuals? In section 19 page 22 there's a troubleshooting guide for the controller. It sounds like you may have a problem with a connector in one of the two plugs going to the controller box. The two plugs come apart to reveal the actual connectors in them and the connectors can be attached individually for testing purposes.
BE CAREFUL!! YOU'RE DEALING WITH 30 AMP CIRCUITS!
The hood switch is an integral part of the circuit, but I THINK it can't cause only one fan to fail.
BE CAREFUL!! YOU'RE DEALING WITH 30 AMP CIRCUITS!
The hood switch is an integral part of the circuit, but I THINK it can't cause only one fan to fail.
07-07-2004, 12:03 PM
#15
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Bill,
I e-mailed the FSM section on troubleshooting the fan system. It didn't scan too well so I can fax it if you like (need number).
Also, just because you have a new (used) controller doesn't mean that it hasn't gone south. There's only about 100 solder connections in the silver controller so any jarring during shipping, etc could give you problems.
Get out your multimeter and do the troubleshooting, it can't hurt and at least in my case, it pointed me at the unit that was problematic (which was the silver controller).
I e-mailed the FSM section on troubleshooting the fan system. It didn't scan too well so I can fax it if you like (need number).
Also, just because you have a new (used) controller doesn't mean that it hasn't gone south. There's only about 100 solder connections in the silver controller so any jarring during shipping, etc could give you problems.
Get out your multimeter and do the troubleshooting, it can't hurt and at least in my case, it pointed me at the unit that was problematic (which was the silver controller).