More Alternator Problems
10-17-2003, 04:37 PM
#16
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Check all possibilites on potential differential. Alt to jump post, alt to battery, battery to jump post, battery ground to engine, frame to engine, battery ground to alt casing, etc.
Starting to run out of ideas. I gree with you that a stcok car should operate as designed with the 90 amp alt. One thing taht wasn't checked by me and I'm not sure if the shop checked, is amp output on the alternator. Everything we did was for checking voltage levels.
Starting to run out of ideas. I gree with you that a stcok car should operate as designed with the 90 amp alt. One thing taht wasn't checked by me and I'm not sure if the shop checked, is amp output on the alternator. Everything we did was for checking voltage levels.
10-17-2003, 04:42 PM
#17
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Jim, are you saying that you can't expect to run all accessories at idle and have the battery charge maintained?
By the way I have tried another ignition box, replaced the green wire, ignition resistors, plug wires and plugs and cleaned and resoddered all wires in the big multipin plug by the jump post.
By the way I have tried another ignition box, replaced the green wire, ignition resistors, plug wires and plugs and cleaned and resoddered all wires in the big multipin plug by the jump post.
10-17-2003, 04:48 PM
#18
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Just an FYI--
The resistor in the excitation circuit determines when your excitation starts. It's between the battery (via the ignition switch) and the voltage regulator. More correctly, it's between the batery and one side of the field coils, while the regumanages at the other end. BUT-- (and there is always a but...), once the alternator is excited by this circuit and it starts making its own current, the resistor does nothing. If you look at a circuit diagram of an alternator, there are six diodes that make three-phse AC current into DC for the battery, and another one to three diodes that take care of maintaining excitation current from the alternator itself.
As others have suggested, you should check the alternator output with an ammeter. More specifically, you should be checking the -voltage- right at the alternator itself, B+ to alternator frame. Do this with lights and wipers, AC, etc, turned on high. Compare that with the voltage you see at the battery between the two terminals under the same conditions, and you'll see how much total voltage drop there is in your wiring and connections. Same test, from the jump-start terminal to the car body (not to the engine) isolates problems that are between that terminal and the B+, and between the car body andf the engine. Move to jump-start terminal and engine, and you've isolated the alternator-to-justart cable and connections. You could quickly isolate the broblem this way, using a structured troubleshooting method and a voltmeter.
Poor/aging wiring and connections can easily fool the voltage regulator, mounted on the alternator, that charging is just fine. Voltage is fine. Meanwhile, at higher current loads, the voltage can easily be lower where the load is, including the ignition system. Chase down and /replace the cables and connections, and you may be good to go for another 25 years.
Folks with electronic injection (post CIS cars) can note that a poor connection to the battery, a poor engine ground cable or connection, and poor connections in the injection circuit can lead to premature injection brain failure. With weak connections, the alternator could be working hard when you change a load in the car. Like when you turn the car off with the headlights turned on. Voltage drop in poor/aging wires makes the alternator work harder into the higher system impedance. Open the ignition and the lights go out, with a spike that could easily overwhelm the thin-film components in the LH brain.
Fopr those that have had LH brain failure, how many can say that A) the problem showed up when I was trying to start the car? And B), how many turned the car off with the headlight switch still on at the end of the previous driving session? The alternator continues to charge while it's turning, even after the ignition switch is turned off. Post your memories/thoughts on this please.
The resistor in the excitation circuit determines when your excitation starts. It's between the battery (via the ignition switch) and the voltage regulator. More correctly, it's between the batery and one side of the field coils, while the regumanages at the other end. BUT-- (and there is always a but...), once the alternator is excited by this circuit and it starts making its own current, the resistor does nothing. If you look at a circuit diagram of an alternator, there are six diodes that make three-phse AC current into DC for the battery, and another one to three diodes that take care of maintaining excitation current from the alternator itself.
As others have suggested, you should check the alternator output with an ammeter. More specifically, you should be checking the -voltage- right at the alternator itself, B+ to alternator frame. Do this with lights and wipers, AC, etc, turned on high. Compare that with the voltage you see at the battery between the two terminals under the same conditions, and you'll see how much total voltage drop there is in your wiring and connections. Same test, from the jump-start terminal to the car body (not to the engine) isolates problems that are between that terminal and the B+, and between the car body andf the engine. Move to jump-start terminal and engine, and you've isolated the alternator-to-justart cable and connections. You could quickly isolate the broblem this way, using a structured troubleshooting method and a voltmeter.
Poor/aging wiring and connections can easily fool the voltage regulator, mounted on the alternator, that charging is just fine. Voltage is fine. Meanwhile, at higher current loads, the voltage can easily be lower where the load is, including the ignition system. Chase down and /replace the cables and connections, and you may be good to go for another 25 years.
Folks with electronic injection (post CIS cars) can note that a poor connection to the battery, a poor engine ground cable or connection, and poor connections in the injection circuit can lead to premature injection brain failure. With weak connections, the alternator could be working hard when you change a load in the car. Like when you turn the car off with the headlights turned on. Voltage drop in poor/aging wires makes the alternator work harder into the higher system impedance. Open the ignition and the lights go out, with a spike that could easily overwhelm the thin-film components in the LH brain.
Fopr those that have had LH brain failure, how many can say that A) the problem showed up when I was trying to start the car? And B), how many turned the car off with the headlight switch still on at the end of the previous driving session? The alternator continues to charge while it's turning, even after the ignition switch is turned off. Post your memories/thoughts on this please.
10-17-2003, 04:58 PM
#19
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Dr. Bob, the difference in voltage between various point in the car (Alt B+, bat, jump post) is negligble, approx .1 or .2 volts. This voltage at idle with no accessories running is about 13.6. Continuity check on grounds is almost perfect, negligible resistance. I have done a lot of work to ensure good electrical connections.
10-17-2003, 05:05 PM
#20
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I suppose if there were high resistance on the circuit supplying the ignition box with power, then a small drop in voltage might have a detrimental effect on the it's operation.
Any thoughts?
Any thoughts?
10-17-2003, 05:15 PM
#21
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Am I correct in assuming that the voltage regulator acts like an on/off switch in applying field current. This switch would be turned on at at the low voltage limit and off at the high voltage limit. Therefore. If I have 13.6 volts at idle (no acc) this is higher than Bat voltage and so the voltage regulator must be functioning.
If that is true then as voiltage drops when accessories are turned on, the VR should turn on the field current at its preset lower limit (maybe 13V, not sure) and the voltage should start to come back up. Of course this assumes that the alternator has the output capacity to bring the voltage backup. In my case it appears that the alt does not have the required capacity.
If that is true then as voiltage drops when accessories are turned on, the VR should turn on the field current at its preset lower limit (maybe 13V, not sure) and the voltage should start to come back up. Of course this assumes that the alternator has the output capacity to bring the voltage backup. In my case it appears that the alt does not have the required capacity.
10-18-2003, 12:14 PM
#22
Sean,
Have you tested the loads for all the accessories? My heater/defrost fan on my 78 5 speed caused a large drop in volts (at the gauge) just before it went out completely. Have you checked the grounds for the headlights? The passenger side is a bear to get to but has probably been neglected for 24 years. Have you checked the connections at the starter? A bad connection at the #50 post on the starter could cause a low voltage to the coil. What is the condition of your positive battery cable? The cables on both of my 78's looked good but had corrosion 8 to 10" up the cable which caused high resistance. Have you cleaned all of the connections (front and back) of the fuse/relay panel?
Sorry I've asked so many questions and not provided an answer.
Dennis
Have you tested the loads for all the accessories? My heater/defrost fan on my 78 5 speed caused a large drop in volts (at the gauge) just before it went out completely. Have you checked the grounds for the headlights? The passenger side is a bear to get to but has probably been neglected for 24 years. Have you checked the connections at the starter? A bad connection at the #50 post on the starter could cause a low voltage to the coil. What is the condition of your positive battery cable? The cables on both of my 78's looked good but had corrosion 8 to 10" up the cable which caused high resistance. Have you cleaned all of the connections (front and back) of the fuse/relay panel?
Sorry I've asked so many questions and not provided an answer.
Dennis
10-19-2003, 12:10 AM
#23
Sean,
1. There are only 2 screws, lower outboard sides, one to outside of the Rheostat wheels -lights & washers. These screws go into slide-on nutplates.
There are three bolts attaching the steering column bridge/cover bottom center of pod. Two of them attach thru the cover wing holes into rivet type barrel nuts. They are 8 or 10mm bolts about 2 1/2" inboard of the two rheostats.
The third might be a screw-mine is missing- just to the left of center , bottom of bridge/cover .
I believe there are 2 more 10mm bolts, one behind and above the ignition switch and one on the opposite side of pod behind and above the fog light switch. They attach to a aluminum offset - 'L' type - which in turn is attached to the instrument cluster assembly.
2. No disassembly needed after removal of the pod with cluster intact.
3. The resistor is centered on a heavy gauge insulated wire.
Either end of the wire is looped and screwed to the PCB behind the Voltmeter -srews are flattips.
In short, getting to the resistor and replacing it should be a small problem, however, there are many wires going to 6 switches which you might not to attempt during Lent. This is the time to change ALL bulbs as they are handy as well.
I've done everything you have done and more... and still have this problem. The only thing I haven't done is swapped out the pin switches on the door jambs. Additionally, when I trickle charge overnight... my brake pressure fault and master fault clear...but...return as I slowly lose charge.
If your VM runs up to 14volts or so I'd say it is an indication that the alt is doing its job trying to replace expended power.
Do as Dernnis suggest's check your wires.
One of the guy's at the Blanco event actually had flicks of his corroded wires from jumper post toward front of engine bundle. Insulation was good but something felt crunchy. He ended-up fabricating an entire loom assembly.
1. There are only 2 screws, lower outboard sides, one to outside of the Rheostat wheels -lights & washers. These screws go into slide-on nutplates.
There are three bolts attaching the steering column bridge/cover bottom center of pod. Two of them attach thru the cover wing holes into rivet type barrel nuts. They are 8 or 10mm bolts about 2 1/2" inboard of the two rheostats.
The third might be a screw-mine is missing- just to the left of center , bottom of bridge/cover .
I believe there are 2 more 10mm bolts, one behind and above the ignition switch and one on the opposite side of pod behind and above the fog light switch. They attach to a aluminum offset - 'L' type - which in turn is attached to the instrument cluster assembly.
2. No disassembly needed after removal of the pod with cluster intact.
3. The resistor is centered on a heavy gauge insulated wire.
Either end of the wire is looped and screwed to the PCB behind the Voltmeter -srews are flattips.
In short, getting to the resistor and replacing it should be a small problem, however, there are many wires going to 6 switches which you might not to attempt during Lent. This is the time to change ALL bulbs as they are handy as well.
I've done everything you have done and more... and still have this problem. The only thing I haven't done is swapped out the pin switches on the door jambs. Additionally, when I trickle charge overnight... my brake pressure fault and master fault clear...but...return as I slowly lose charge.
If your VM runs up to 14volts or so I'd say it is an indication that the alt is doing its job trying to replace expended power.
Do as Dernnis suggest's check your wires.
One of the guy's at the Blanco event actually had flicks of his corroded wires from jumper post toward front of engine bundle. Insulation was good but something felt crunchy. He ended-up fabricating an entire loom assembly.
10-19-2003, 01:37 PM
#24
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Thanks Dennis & John. It apparent that I will have to delve much deaper into this problem. E.g. some new wiring and cleaning everything I can in the pod.
I have aready fabricated a new harness for the the top of the engine which took care os some gremlins. I have also cleaned all the ground point on the car, inlcuding the tough one in the rear hatch area. Ckecks of voltage differential beteen battery, alt and jump post have shown no problems. However, havn't check at starter motor connections.
Have either of you had the problem of decaying idle when the voltage drops too low?
Thanks
I have aready fabricated a new harness for the the top of the engine which took care os some gremlins. I have also cleaned all the ground point on the car, inlcuding the tough one in the rear hatch area. Ckecks of voltage differential beteen battery, alt and jump post have shown no problems. However, havn't check at starter motor connections.
Have either of you had the problem of decaying idle when the voltage drops too low?
Thanks
10-19-2003, 02:56 PM
#25
Sean,
I expect that the decaying idle is due to low voltage to the #15 post at the coil. It needs a minimum of 3 volts to properly fire. Considering the power goes through a .6 and .4 ohm resister, a drop below 10 volts to the resistors will cause a weak spark.
Dennis
I expect that the decaying idle is due to low voltage to the #15 post at the coil. It needs a minimum of 3 volts to properly fire. Considering the power goes through a .6 and .4 ohm resister, a drop below 10 volts to the resistors will cause a weak spark.
Dennis
10-19-2003, 02:57 PM
#26
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Sean,
Have you also cleaned the ground strap from the engine to the chassis?
This is placed beside the right engine mount - I cleaned this in connection with an engine change and after this, all electrical problems disappeared!!!
Other tips:
1. The resistance on the back of the cluster can easily be simulated by a 3-5W bulb mounted at terminal O8 at the central board -
2. The regulator can be improved by placing a diode between the regulator and the generator - I cannot remember 100% what terminals, but an electric mechanic will know - This diode 'cheat' the regulator, I think with 2.4 V - I.e. 'telling the regulator that the voltage is 2.4 V lover than actual (When I bought my car back in 1995 I had similar problems, and then the Bosch garage placed this diode as a guaranty repair)
But I think the best and most important tip is the ground straps!
I am sure Wally can say mush more about this - I am not an electrician
Have you also cleaned the ground strap from the engine to the chassis?
This is placed beside the right engine mount - I cleaned this in connection with an engine change and after this, all electrical problems disappeared!!!
Other tips:
1. The resistance on the back of the cluster can easily be simulated by a 3-5W bulb mounted at terminal O8 at the central board -
2. The regulator can be improved by placing a diode between the regulator and the generator - I cannot remember 100% what terminals, but an electric mechanic will know - This diode 'cheat' the regulator, I think with 2.4 V - I.e. 'telling the regulator that the voltage is 2.4 V lover than actual (When I bought my car back in 1995 I had similar problems, and then the Bosch garage placed this diode as a guaranty repair)
But I think the best and most important tip is the ground straps!
I am sure Wally can say mush more about this - I am not an electrician
10-19-2003, 03:14 PM
#27
Sean,
A few years ago (15 ) my 924 alternator was going through regulators. Took it to an auto electric shop who put a self exciting regulator on it. Drove it another 13 years without a problem. You may want to check the shops in your area to see if it is still available.
Dennis
A few years ago (15 ) my 924 alternator was going through regulators. Took it to an auto electric shop who put a self exciting regulator on it. Drove it another 13 years without a problem. You may want to check the shops in your area to see if it is still available.
Dennis
10-19-2003, 03:58 PM
#28
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Thanks, everybody. The ground strap connections between engine and chassis have been cleaned. Also, I beleive that my alternator is already self exciting. However, if anyone knows differently let me know.
The cheat on the alt sound interesting Wouldn't you install a resistor though??
I will check the the voltage at the coil.
Glad to know I am not alone with these type of problems.
Thanks
The cheat on the alt sound interesting Wouldn't you install a resistor though??
I will check the the voltage at the coil.
Glad to know I am not alone with these type of problems.
Thanks
10-19-2003, 04:36 PM
#29
Sean,
If you have the standard regulator it needs the exciter source. On my 924 (may be different) I had to run an ignition switched battery sourced wire to the exciter contact.
Dennis
If you have the standard regulator it needs the exciter source. On my 924 (may be different) I had to run an ignition switched battery sourced wire to the exciter contact.
Dennis
10-20-2003, 01:51 PM
#30
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I just put a Bosch on my car and got rid of that POS French alternator. All is good thus far.
The local shop had an old rebuild for $85.00, this was after I gave another shop $82.00 to put a new regualtor on the POS French unit, then a week later the diode pack blew out of it.
The French alternator is now in the trash, they didn't even want it for a core.
The local shop had an old rebuild for $85.00, this was after I gave another shop $82.00 to put a new regualtor on the POS French unit, then a week later the diode pack blew out of it.
The French alternator is now in the trash, they didn't even want it for a core.