Voltage from alternater won't stay steady (video)
10-21-2012, 10:31 PM
#23
it most likely is not the alternator nor the voltage regulator especially if you had those replaced and if you had the alternator bench tested and it showed fine.
And to say the stock alternator is garbage or that you "need" to buy the truck alternator to fix the problem is very silly. Millions of cars on the road with stock alternators that are fine.
is your car stock? did you ever do any motor work where you would have messed with electrical wiring to the alternator? the way the PCM controls the alternator has varied over the years, one thing that comes to mind is the 1998 alternator wiring connection was different than the later years. I believe the computer sent a 12v signal to the voltage regulator to turn the alternator on versus a 5v signal for the later years (but don't quote me on that). but if nothing like that is the case, generally when the gauge bounces like that it's due to a failed diode in the rectifier in the alternator. That converts AC to DC and gives you a steady DC voltage. When one or more diode fails you see AC ripple, you can see pulsation in all the lights but i've never seen it such that the gauge bounces like yours because of that. And the frequency of the pulsation would get faster with rpms, and basically disappears or is so high you can't tell. So i don't think it's a diode/rectifier problem. What i would do is get a voltmeter, preferably an analog one with a needle which will verify there is a voltage bounce. A digital voltmeter most likely won't catch it but you could try. This would rule out the volt gauge in the cluster. Only other thing i can think of is bad stepper motor in the gauge cluster, or you have a bad gauge cluster.
other thing i meant to say was regarding the shop who replaced the voltage regulator. There are all kinds of regulators and there is a chance they used the wrong one and the external wiring connector from the pcm to the alternator is not matching the regulator- going back to what i was saying about 1998 reg's getting a 12v turn on signal vs later years using 5v. In my opinion best thing to do is go to napa, autozone, and get a whole new alt. for your vehicle and save yourself the time and aggravation, and get one with a lifetime warranty. it's just not worth it anymore to have alternators or starters rebuilt at a shop. only other thing i can think of is you have a bad/loose connection going to the alternator or you have a bad/corroded ground somewhere and the regulator is working properly and sensing the connection and trying to compensate for it.
And to say the stock alternator is garbage or that you "need" to buy the truck alternator to fix the problem is very silly. Millions of cars on the road with stock alternators that are fine.
is your car stock? did you ever do any motor work where you would have messed with electrical wiring to the alternator? the way the PCM controls the alternator has varied over the years, one thing that comes to mind is the 1998 alternator wiring connection was different than the later years. I believe the computer sent a 12v signal to the voltage regulator to turn the alternator on versus a 5v signal for the later years (but don't quote me on that). but if nothing like that is the case, generally when the gauge bounces like that it's due to a failed diode in the rectifier in the alternator. That converts AC to DC and gives you a steady DC voltage. When one or more diode fails you see AC ripple, you can see pulsation in all the lights but i've never seen it such that the gauge bounces like yours because of that. And the frequency of the pulsation would get faster with rpms, and basically disappears or is so high you can't tell. So i don't think it's a diode/rectifier problem. What i would do is get a voltmeter, preferably an analog one with a needle which will verify there is a voltage bounce. A digital voltmeter most likely won't catch it but you could try. This would rule out the volt gauge in the cluster. Only other thing i can think of is bad stepper motor in the gauge cluster, or you have a bad gauge cluster.
other thing i meant to say was regarding the shop who replaced the voltage regulator. There are all kinds of regulators and there is a chance they used the wrong one and the external wiring connector from the pcm to the alternator is not matching the regulator- going back to what i was saying about 1998 reg's getting a 12v turn on signal vs later years using 5v. In my opinion best thing to do is go to napa, autozone, and get a whole new alt. for your vehicle and save yourself the time and aggravation, and get one with a lifetime warranty. it's just not worth it anymore to have alternators or starters rebuilt at a shop. only other thing i can think of is you have a bad/loose connection going to the alternator or you have a bad/corroded ground somewhere and the regulator is working properly and sensing the connection and trying to compensate for it.
Last edited by 1 FMF; 10-21-2012 at 10:42 PM.
10-22-2012, 05:04 PM
#24
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it most likely is not the alternator nor the voltage regulator especially if you had those replaced and if you had the alternator bench tested and it showed fine.
And to say the stock alternator is garbage or that you "need" to buy the truck alternator to fix the problem is very silly. Millions of cars on the road with stock alternators that are fine.
is your car stock? did you ever do any motor work where you would have messed with electrical wiring to the alternator? the way the PCM controls the alternator has varied over the years, one thing that comes to mind is the 1998 alternator wiring connection was different than the later years. I believe the computer sent a 12v signal to the voltage regulator to turn the alternator on versus a 5v signal for the later years (but don't quote me on that). but if nothing like that is the case, generally when the gauge bounces like that it's due to a failed diode in the rectifier in the alternator. That converts AC to DC and gives you a steady DC voltage. When one or more diode fails you see AC ripple, you can see pulsation in all the lights but i've never seen it such that the gauge bounces like yours because of that. And the frequency of the pulsation would get faster with rpms, and basically disappears or is so high you can't tell. So i don't think it's a diode/rectifier problem. What i would do is get a voltmeter, preferably an analog one with a needle which will verify there is a voltage bounce. A digital voltmeter most likely won't catch it but you could try. This would rule out the volt gauge in the cluster. Only other thing i can think of is bad stepper motor in the gauge cluster, or you have a bad gauge cluster.
other thing i meant to say was regarding the shop who replaced the voltage regulator. There are all kinds of regulators and there is a chance they used the wrong one and the external wiring connector from the pcm to the alternator is not matching the regulator- going back to what i was saying about 1998 reg's getting a 12v turn on signal vs later years using 5v. In my opinion best thing to do is go to napa, autozone, and get a whole new alt. for your vehicle and save yourself the time and aggravation, and get one with a lifetime warranty. it's just not worth it anymore to have alternators or starters rebuilt at a shop. only other thing i can think of is you have a bad/loose connection going to the alternator or you have a bad/corroded ground somewhere and the regulator is working properly and sensing the connection and trying to compensate for it.
And to say the stock alternator is garbage or that you "need" to buy the truck alternator to fix the problem is very silly. Millions of cars on the road with stock alternators that are fine.
is your car stock? did you ever do any motor work where you would have messed with electrical wiring to the alternator? the way the PCM controls the alternator has varied over the years, one thing that comes to mind is the 1998 alternator wiring connection was different than the later years. I believe the computer sent a 12v signal to the voltage regulator to turn the alternator on versus a 5v signal for the later years (but don't quote me on that). but if nothing like that is the case, generally when the gauge bounces like that it's due to a failed diode in the rectifier in the alternator. That converts AC to DC and gives you a steady DC voltage. When one or more diode fails you see AC ripple, you can see pulsation in all the lights but i've never seen it such that the gauge bounces like yours because of that. And the frequency of the pulsation would get faster with rpms, and basically disappears or is so high you can't tell. So i don't think it's a diode/rectifier problem. What i would do is get a voltmeter, preferably an analog one with a needle which will verify there is a voltage bounce. A digital voltmeter most likely won't catch it but you could try. This would rule out the volt gauge in the cluster. Only other thing i can think of is bad stepper motor in the gauge cluster, or you have a bad gauge cluster.
other thing i meant to say was regarding the shop who replaced the voltage regulator. There are all kinds of regulators and there is a chance they used the wrong one and the external wiring connector from the pcm to the alternator is not matching the regulator- going back to what i was saying about 1998 reg's getting a 12v turn on signal vs later years using 5v. In my opinion best thing to do is go to napa, autozone, and get a whole new alt. for your vehicle and save yourself the time and aggravation, and get one with a lifetime warranty. it's just not worth it anymore to have alternators or starters rebuilt at a shop. only other thing i can think of is you have a bad/loose connection going to the alternator or you have a bad/corroded ground somewhere and the regulator is working properly and sensing the connection and trying to compensate for it.
Several things though, a quick look at my signature will reveal my car is not stock and not a 98 model. The problem just randomly started when the car sat for about 2 months while I had the transmission and rear end pulled. It is definatly not a gauge issue because every light on the car reflects the varying voltage, when driving at night you can physically see the headlights getting brighter and dimmer. There is no bad connection on the alternator, I've had it on and off too many times to not notice that. The only other thing that I see it could be is maybe a bad or corroded ground wire somewhere else on the car, but I've yet to find it. I still stand by my statement that it is a bad part in the Alt, like I said earlier, while the car was running I disconnected the battery and the car died.
10-23-2012, 10:29 AM
#25
you have a 2002 ws6 correct?
I have the service manual for 2002 and i've looked in the past but can't remember if it details the wiring to the alternator. How many wires in the plug going to the alternator, not counting the large output wire that's all by itself? I thought it can be anywhere from 2 to 4 wires. One wire is the 5 volt turn on signal from the PCM. if you can probe into the wire with a meter and see if that 5v is going 5v to 0v to 5v, that would tell you the pcm is commanding the alternator off for some reason. another wire is the 12v reference wire which runs into the wiring harness and connects to the positive side of the electrical system somewhere near the battery, if this wire has a bad connection or high resistance the alternator will output higher voltage thinking the system voltage is low. my guess is you have some electrical connection problem given you had the trans and rear out. hopefully it's not something like mice chewing on wires. but it looks like the PCM is monitoring the alternator output, recognizes a problem then commands the alternator off by running 0v on the turn on wire to the alternator. then it commands it on again until it sees a problem then shuts it off to prevent damage. i would think this would set a DTC and check engine light. normally if it's a bad part in the alternator the alternator does not output at all. There are other ways to troubleshoot alternators such as jumping the regulator so it gets full field current and outputs 100% all the time but i only know how to do that on older 10si alternators not late model ones.
http://oljeep.com/gw/alt/edge_Altern...html#Section_3
see about 2/3 down, S, F/I, L, P terminals regarding the voltage regulator.
Last edited by 1 FMF; 10-23-2012 at 12:03 PM.
10-23-2012, 04:50 PM
#26
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Beside the main wire coming from the alternator there is just a 4 pin connector that only has one wire on it. There are not and never have been mice on my car, there are no check engine lights and the car runs extremely well performance wise.
I disagree about disconnecting a battery while an engine is running. If an alternator is not charging (therefor it cannot supply voltage to run the engine) and the battery is un hooked while the engine is running the engine and electronics will not have 12V to stay running and the engine will die.
I disagree about disconnecting a battery while an engine is running. If an alternator is not charging (therefor it cannot supply voltage to run the engine) and the battery is un hooked while the engine is running the engine and electronics will not have 12V to stay running and the engine will die.
10-23-2012, 05:02 PM
#27
I think he was referring to the exciter wire (the single wire on the 4 pin connector) voltage. I'm not sure where that reference comes from but thought it was delivered via the PCM. In that case, it should not matter if the battery is hooked up or not. By the logic above, we wouldn't be able to run the car or jump it with a dead battery...
10-25-2012, 12:32 PM
#28
you did not read my link.
http://oljeep.com/gw/alt/edge_Altern...html#Section_3
do you have a part number for your voltage regulator you had installed?
for your volt gauge to bounce like it did in the video, it looks like the alternator is being turned on and off by the PCM and it is being done for a reason. I'm guessing you either have the wrong voltage regulator installed, you said you had a shop install just that so it's very possible they used the wrong one. Or the voltage reg. is bad and that is possible if you disconnected the battery with the engine running. Having a 1 wire alternator simplifies things, and i believe it's just the turn on signal to tell the voltage regulator to output. whether it's a solid 5v, or solid 12v, or PWM 5v signal i don't know.
http://oljeep.com/gw/alt/edge_Altern...html#Section_3
Since these CS-series regulators are now essentially an electronic computer chip, so always disconnect the battery before servicing, and do not EVER remove the battery cable when the engine is running. If you simply must do this, you may have just destroyed the regulator’s computer chip. You must really begin to think of these alternators as computers, and treat them with the respect that you might a laptop computer.
for your volt gauge to bounce like it did in the video, it looks like the alternator is being turned on and off by the PCM and it is being done for a reason. I'm guessing you either have the wrong voltage regulator installed, you said you had a shop install just that so it's very possible they used the wrong one. Or the voltage reg. is bad and that is possible if you disconnected the battery with the engine running. Having a 1 wire alternator simplifies things, and i believe it's just the turn on signal to tell the voltage regulator to output. whether it's a solid 5v, or solid 12v, or PWM 5v signal i don't know.
10-25-2012, 01:23 PM
#29
The stuff inside our alternators is not that fragile or sophisticated.
02-07-2013, 04:47 PM
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I know it's a late update, I sold the car last month, but before I sold it I picked up an alternator from an 03 suburban for $45 from a local salvage yard, all I had to do was lengthen the single wire on the 4 pin connector and put it on and it fixed the issue. Hopefully this can help anyone else that haves the problem.
02-09-2013, 12:28 PM
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Unforntueatly what you experienced was a bad alternator. They can test good on the bench but in service is a completely different setup. I've seen it many many times myself. My 02 had the same trouble, I pulled it and tested everything in it and it all passed testing good. Replaced the alt with a new GM alt and no more issues.
Unfortunately when you buy a rebuilt alt you get the same trouble because the old parts passed testing.
The rotor windings can fail as they heat up and spin. NOWAY to test it on the bench like its being used in service.
Unfortunately when you buy a rebuilt alt you get the same trouble because the old parts passed testing.
The rotor windings can fail as they heat up and spin. NOWAY to test it on the bench like its being used in service.
