High voltage from alternator is overheating the battery

VIRGIL SHELTON II

MEMBER
2002 CADILLAC DEVILLE
V8
2WD
AUTOMATIC
110,000 MILES

Alternator is pushing 15 volts, cooking my battery. I believe a prior electrical problem exists because seller just replaced alternator one moth ago. I have a better understanding then most of Auto Technology, but by no means am I a professional. Since prior problems existed, and with dash codes I believe I have problems with my RIM module and my PCM module, to my understanding my PCM module controls my volt regulator of my alternator? Rather than spend tons of money, I am willing to accept failure of all most all interior power, I only want to reduce or use the extra volts my alternator is producing, so in return my battery does not cook. How can I reduce or spend the volts so this happens? A capacitor? Running another battery?

Thursday, April 25th, 2019 AT 7:51 PM

5 Replies

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

You could run a 2 volt light bulb in line from the alternator to the battery. If you want to fix the problem correctly, we will be here with specific instructions on how to fix the problem. Please, don't hesitate to ask, it's what we do, and what we are here for.

Thanks,
Alex
2CarPros

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Thursday, April 25th, 2019 AT 8:53 PM

VIRGIL SHELTON II

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4 POSTS

Where would a find a 2 volts light bulb?

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Thursday, April 25th, 2019 AT 9:06 PM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello again,

In the diagrams down below I have included four different diagnostic troubleshooting guides for various Direct Trouble Codes (DTC)(s), all involving to high voltage from the alternator. There are a couple of charging system troubleshooting guides as well. Please go through these guides and get back to us with what you are able to find out, please.

Thanks,
Alex
2CarPros

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Friday, April 26th, 2019 AT 2:24 AM

VIRGIL SHELTON II

MEMBER
4 POSTS

A lot of tests I can't do. AutoZone says their scan tool won't read anything unless engine light is on. All other dash lights are, but not that. Was told alternator tests fine, but pushing 15 volts, battery reads 12 volts sitting, drove it again just now, after five minutes horrible smell, heat, and boil over. I don't have money to fix this the proper way right now. Can someone please tell me a trick to divert some volts away from my battery? Capacitor? Another car battery? A PCM bypass trick?Please help

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Friday, April 26th, 2019 AT 5:01 AM

ASEMASTER6371

MECHANIC
52,797 POSTS

Good afternoon,

There is no trick or bypass for the charging system.

The generator is what maintains the battery. It has the regulator inside which keeps the alternator from overcharging.

If you have a voltmeter, make sure you have power to the orange wire at the alternator connector. It is fused controlled.

Beyond that, I would remove the alternator and take it to a parts store and have them check the part. It is a free service. That will tell you if it is the alternator or the PCM which controls turning on and off the regulator.

Roy

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