Nicholbry

Wally, no apologies necessary as I'm not very knowledgeable about using a multimeter. I should apologize for not knowing more than the average Rennlister about this stuff. I'm trying to understand, however. Your info. was helpful.

Alan...just forget the previous post with values as I was getting the same reading as below...just referencing the wrong mark on the dial. Hopefully, this will help you, to help me, better:

Using the multimeter (see my pic), with what appears to be the lowest setting under DCV (50) that will register the volt range expected, I grounded the black lead from the multimeter on a hex screw mounted up high in the fuse compartment that had several brown wires connected to it. I also contacted the installed fuses (#29 & #30) with the "+" at their indents; first the top and then the bottom.

The results:
* 12 - 12.5 mark on both fuses at both their indents (top/bottom) with the ignition off. The reading was basically the same with the engine cranked and AC running.

* 12 - 12.5 mark on terminals 1 & 4 at the final stage connector with the ignition off.

Thanks for your patience while trying to help out such a rookie as myself.

Nicholas

Nicholbry

Also, I'm going through the "Troubleshooting" section for the engine cooling in the WSM as best I understand.

Disconnected the I and II plugs from the control unit between the pass. seat and door and did the following:
1.) Test voltage supply: pin 2 & 7 (seems ok)
2.) pin 4 and 7 (reading voltage w/ ignition on per instructions - ok)
3.) Function test of the AC button pin 7 (plug I) and pin 5 (plug II) and reads voltage - ok

However, at the very end of the "Troubleshooting" I don't get the 7v reading that they say I should have. It may be that I don't quite understand the instructions when it says "Measure the voltage with an analog voltmeter with an external resistance (Ri) 100 kOhm". Maybe I just don't understand what they mean by "external resistance". Given the picture that I provided above can you walk me through it (what setting to use for the multimeter) and perhaps your own version of how to vs. the WSM?

Plug II was reconnected as it is in the instructions (as well as the output stage connector). I tried taking the measurement with it on a variety of the DCV settings between 2.5 - 10 - 50 - 250, with the ignition on and AC button depressed; but no reading. Do I have my multimeter on a wrong function (i.e. DCV instead of something else)? Or is this the culprit?

Thanks again,
Nicholas

Alan

The output stage needs a load (like the fan or at least a minimum resistance instead) - it wont work correctly into an open circuit. 7v is presumably the 1/2 speed drive voltage...

Alan

Nicholbry

So, I'm unclear. In your reply, does this suggest I have a problem with the control unit, output stage, or not necessarily a problem?

Any ideas from where I'm at now as to my culprit? Where should I look to next?

Thanks again Alan.

Nicholbry

Anyone care to take a guess or suggest where (and how) I might look next towards sourcing my problem.

Recap:
- Pass. side fan isn't working as I'm getting no voltage there
- The plug appears to be in good shape (bright contacts, no evidence of burning/overheating)
- The plug from the functioning fan operates the pass. side fan (so it's not the fan motor)
- Clicking noise (previously mentioned) in/or around the fuse panel or under the console persists
- The good fan operates at a higher pace than before with brief power dives
- Wires seem to be intact as best I can see (also at the battery)
- #29 & #30 fuses are good and getting voltage readings there
- Checked pin 1, 4, & 2 at the output-stage and I'm getting a voltage there
- Voltage tested OK on control unit at pins 2 & 4
- Flap fuse has been removed and was zip tied shut years ago
- I didn't get a reading of the required 7v when function-testing the control signal of the output stage at the control unit (per instructions in the WSM). However, I may not have done it correctly as I'm still unclear how to create the "external resistance (Ri) 100 kOhm" per the instructions.

I'm hoping to avoid having to drive my car with a bum fan in 92+ degree weather an hour to the nearest mechanic who has limited knowledge of Porsche 928s.

Thanks for any help!

Herman K

I had the roller bearing on one of the fans lock up from time to time by reversing the spinning direction I could free it up but it still didn’t sound healthy compared to the other. I opted to get one new fan and replace the bearings as seen in a recent thread. While waiting for the new fan to arrive I disassembled the old ones for inspection one indeed had failed bearings (sloppy feel and sounding bad when rotating by hand) the other the bearing did spin fine and sounded ok but I found that the inner race of this bearing didn’t not sit very tight on the shaft ( I know when I remove the bearing from the shaft I can expanded the shaft metal so it will fit tight again) but I opted to order a second new fan instead. I reasoned that these fans are very critical in the overall operation of the vehicle and that after 15 years of service I would be better of to spend the money now than to be sorry later. I have cleaned up all my connectors and all the issues (just like yours) have disappeared no more fan related issue and on top of that the temperature gauge shows about two needle widths less.

Good luck in your resolve

Nicholbry

Thanks Herman. When using the plug from the other fan it operates fine (without any evidence of fail...i.e. bearings, etc.). Therefore, I don't imagine my issue is the same as your experience. I appreciate you trying to offer an option, nonetheless.

Anyone else care to offer a potential cause?

Kindest regards,
Nicholas

dr bob

Nicholas--

Go back to the battery. Remove and clean ALL the connections on the positive terminal, as well as the main connection to the battery post. Clean until the metal is bright and shiny, using a wire brush or some fine sandpaper. Those smaller red wires are for the cooling fans, One to each fan) and to the fuel injection and fuel pump. A slightly dirty or corroded connection will cripple the car, so make sure they are really clean and that the bolt there is tight. Once all is reassembled and tight, add a coating of Vaseline to the metal to prevent later corrosion.

I have seen only one valid case of a controller failure, and that was the black box on the front apron. It's easy enough to plug your controller into another car to test it, if you have another S4+ owner somewhere near where you are.

Nicholbry

Dr. Bob....thanks for your reply. I will do as you say with the battery despite it looking very clean. A couple years ago a new + cable was installed (heavy duty) and a side post for the smaller red lines that lead to the fans, etc. It was coated with a battery spray protectant (liberally) and there is no obvious sign of insult. However, you could very well be right as it doesn't take much to disrupt a contact.

I'm starting to lean towards stripping some wire back near the connector at the fans to see if the wires are hot (perhaps it is the connector that is gone despite the contacts inside looking bright). If that doesn't work, I'm suspecting the output-stage.

Unfortunately, I don't have anybody close that could let me use their output-stage to test it out. Because this could turn into an expensive fishing trip, I'm trying to avoid buying one until I am more certain it is the problem ($150 used). I was courting the idea of posting a thread asking for a loaner, but I'm going to dig a bit more for the cause before publicly announcing myself as a "bum".

I find it more than coincidental that this occurred after having the fan out of the car, the radiator drained, moving the radiator around (up/down) a bit to get access to the lower mounts to replace, trimming the fan shroud a bit at the radiator tabs, etc. I replaced the coolant, the wires were safely zip-tied out of the way while this was going on and they were reconnected the exact fashion they were removed without any problem. Everything seemed to button back up just as it was removed. I'm thinking I must have done something to cause this because of the timing.

I looked (as best I could) at the electric sensor on the front, lower, left side of the radiator and there doesn't visually seem to be anything unusual about it. I'm curious; however, could a problem with it cause a single fan to not operate?

Thanks again for your help...and anyone else who cares to put their $0.02 in.

With much appreciation,
Nicholas

Giovanni

Nicholas, post a pic of the item and I will send you a loaner. If its easy to get to and you post the pic tonight, I can get it in the mail tomorrow morning.

Nicholbry

Oh WOW Giovanni. I thank you for that....very generous. Here's the pic and I'm sending you a PM with my shipping info. Sorry for the late evening post with the pic.

I'm anxious to see if this remedies my problem.

I'll gladly send you shipping $$. No rush to get it out in 24 hrs. I will be out of town until Monday of next week anyway. Thank you again....it means alot to this guy who's been sweating in this summer heat bangin' my head against the wall trying to sort this frustrating problem.

Giovanni

Hey Nicholas,

It was shipped this morning with USPS so you should have beginning of next week. I hope it fixes your problem and if not, just send it back.

Thanks,

Nicholbry

You rock

Nicholbry

I received Giovanni's output stage in the mail yesterday evening and I put it on today. That was the problem after all. Both fans are working as they should now. I hit it was a light coat of high temp black paint and the part looks (and operates) as good as new.

I was humbled by Giovanni's generosity in loaning the part. Your funds have been sent Gio!

Thanks also to Alan for his many posts trying to help me troubleshoot my problem. Thanks also to the rest of you guys who posted your helpful comments (Herman, Wally, Dr. Bob, etc).

Kindest regards,

Alan

OK great that you solved it. I'll put that one in the 'other' column - usually the output stages are very reliable - I've heard of very few that have failed - but there are always some random failure issues.

It doesn't seem like an obvious weak spot on a 928 though. (of course now we will have a rash of failures to prove me wrong.. )

Alan