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Service charging system and battery light on

Tiny
JON HELMBRECHT
  • MEMBER
  • 2001 CADILLAC ELDORADO
  • V8
  • 2WD
  • AUTOMATIC
  • 79,000 MILES
Had alternator tested said voltage regulator failed. Bought new alternator put it in put it all back together battery light still on service charging system still on. Took new alternator back out brought it to O'Reilly's I had it tested failed. So did I get a faulty alternator or is my car burning alternators? They said it could possibly be the clip and the alternator? Aftermarket has three wires four prongs mine has two wires all the way back to main harness and no splices an only two prongs. What the heck!
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Wednesday, September 23rd, 2020 AT 5:18 PM

5 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Your connector is correct. You have two wires on the connector and should have a B+ wire coming from the battery.

Take a look at the wiring diagram. I doubt the vehicle is damaging the alternators but clearly we need to test this with a known good alternator installed.

As for the aftermarket being different that is most likely just due to them not wanting to make a different one for this vehicle. Basically the other terminals just would not be used.

Did you install the new replacement and get the same thing?
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Wednesday, September 23rd, 2020 AT 5:43 PM
Tiny
JON HELMBRECHT
  • MEMBER
  • 3 POSTS
I bought a new refurbished alternator from O'Reilly's and installed it put everything back together service charging system light and battery light still on. Took it out of the car brought it back to Riley's they put it on their tester and it completely failed on all levels. They warrantied the new one out. I pick up another new one tomorrow morning. They said they would put it on the tester and see if it's good and passes before I install it this time, but they said if there's an issue with your car burning them out they will not warranty it again. I'm out my money so kind of scared to put it in. I have not done anything with the wiring harness it looks good, no burn marks or melts. Sorry I am clueless when it comes to that diagram. " There is one big red wire about the thickness of a pencil going from the battery that bolts to the peg on the side of the alternator.
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Wednesday, September 23rd, 2020 AT 5:48 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
I understand. However, the only thing that would cause this is the voltage regulator that doesn't turn off the magnetic field and the voltage grows to large. Even though I have seen this happen, it normally causes things to melt like the wiring and will even damage the PCM where the regulator is.

So if you don't have melted wiring then I suspect you will be fine.

If you want to, install the alternator and then put a meter on the battery when you start the engine. If it gets over 15 volts, shut the vehicle off and we can check the PCM.

Here is how this system works if you would like to read about it.
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Thursday, September 24th, 2020 AT 5:38 PM
Tiny
JON HELMBRECHT
  • MEMBER
  • 3 POSTS
So I got another alternator from O'Reilly's they tested it before I left and it's good put it all in hook it all back up still says charge system light and battery light on put a voltmeter on the battery has 12.2 not running start it up and it stays at about 11.8 does the wiring harness with the two wire connector that goes into the alternator does that have a power source? I bought a new refurbished alternator from O'Reilly's and installed it put everything back together service charging system light and battery light still on took it out of the car brought it back to Riley's they put it on their tester and it completely failed on all levels. They warrantied the new one out I pick up another new one tomorrow morning they said they would put it on the tester and see if it's good and passes before I install it this time but they said if there's an issue with your car burning them out they will not warranty it again and I'm out my money so kind of scared to put it in I have not done anything with the wiring harness it looks good no burn marks or melts sorry I am clueless when it comes to that diagram. " There is one big red wire about the thickness of a pencil going from the battery that bolts to the peg on the side of the alternator"?
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Friday, September 25th, 2020 AT 6:35 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
No. There is no power source. More then likely the PCM is the issue. We need to check voltage on the L terminal which is the Turn on signal from the PCM. I attached the OEM diagram that gives a little more detail on how this works. Then I attached the circuit description so that we can figure this out.

Basically if the alternator is not getting turned on then it will cause the engine to run off the battery and that explains the voltage.

So let's check voltage here when the engine is running and go from there.
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Saturday, September 26th, 2020 AT 7:33 PM

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