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1990 Cadillac Seville
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20 Posts
Discussion Starter #1
All right. I wish I could have my car home right now to do some diagnostics, but it's stuck on the side of the road.

First off, I will say it is a 1991 Cadillac Seville that seems to carry tons of electrical gremlins. Earlier last week I had been working on tracing these down and sorting them all out. I found a few shorts, replaced the alternator, and replaced a coolant sensor.

The battery was still draining every night and so I would throw the charger on it at night and just disconnect the battery when I got to school. I did this for about four days.

On the way to school this morning, the service engine soon light came on. It's nearing the 145,000 mile mark and so I figured it was triggered by mileage. Arrive at school, with outside of its usual quirks showing up. Disconnected the battery and headed on in.

Come this afternoon when I pop the hood and connect the battery terminals and I find it won't turn over. I get a jump start from a friend and head on my way to work. I'm driving along and things appear to be normal. All of a sudden, the instrument panel goes out, the driver information center goes out, and then they start to flash on and off.

I decide to make the leap of faith and try limping it home. It made it about 300 feet down the road before it started to chug and die. I pulled off to the shoulder and called a friend to get a ride to work.

I get done with work and my brother and I get a ride out to the car. We try getting it started once again. We got it to turn over and idle for a while. Unfortunately, it started to chug down again in about ten seconds. We tried to jump it again, but no dice. We shut the windows up and left it sitting there until we can work something out to get it home.

I don't know where to start looking, so I come to you, my fellow gearheads, for some assistance in the diagnosis. I wish I had it here so I could go into the diagnostics mode and check the codes, but I'm dying to know now.

Also, I am not set on getting it to run again at all. If I can for a reasonable amount, I'll consider it, but I have a feeling it's going to be a matter of stripping it down figuring out what caused it, and scrapping it.
 

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1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
Sounds like your alternator isn't giving your battery a good charge. EIther the cables going from the alternator are bad, the belt isn't adjusted right, or most likely the alternator is shot. Usually the dash will flash when it goes bad. Your other electrical issues are probasbly due to having such low voltage in the battery. I'd go get yourself a new battery and alternator.
 

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94 ETC,97 STS
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3,531 Posts
If you disconnected the battery and reconnected it a few hours later and it was dead then it's DEAD!

I'd say a new battery is the first thing to get. Thoroughly clean all the battery connections.

Check voltage when running. It should be in the 14volt range. If it's 12.9 or less the alternator is not working properly.

The rectifier in the voltage regulator can lose 1 diode and not give an indication of failure but it is not putting out enough amperage to charge the battery. It will put out enough voltage with no load but not with a load.
 

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1990 Cadillac Seville
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20 Posts
Discussion Starter #4
I finally got the car home. I was just probing around with my DVOM this evening. It looks like my alternator is doing a hilariously poor job, and so I'll bring it in and get a new one under their warranty. The cables are all fine as far as all the continuity and resistance testing tells me.

I feel that while I'm at it I may as well check the voltage regulator too. Where is it located on this vehicle? I've looked at various wiring diagrams online and they have shown nothing. From looking at the schematics, it seems the BCM does the voltage regulation. What gives?

Also, thank you all for the help thus far.
 

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99 Seville STS, 08 STS4 N* 1SG F55
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3,516 Posts
The voltage regulator is part of the alternator. I don't recall BCM being involved in the charging circuit but its been awhile.
 

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1990 Cadillac Seville
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20 Posts
Discussion Starter #6
I do indeed need to replace the alternator which will take care of any problems with said voltage regulator. Excellent.

Here's the diagram I've been using for the charging circuit:

http://download.yousendit.com/42B35E7703D8FA25

Maybe I'm not interpreting it quite right, but it does seem that it may have some control.
 
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