Red Battery Light Issues | ‘98 MGM

[_Hacksaw]

I’m back after an extended absence of any problems with my beautiful ‘98 MGM.

Briefly my red battery light comes on and then goes off without any adverse or incidental malfunctions or warnings. No ‘Check Engine’ light or code requests etc.

It does not follow any high current draw pattern so I’m a bit stumped at present.

Where to start with this critter? Bad diode in the alternator? No flicker in the dome or dash lights yet.

Bad connection at the alternator or corrosion and thus a high resistance region there?

Kinda stumped at present but it’s nothing compared with replacing the battery on my iPhone 5s recently that took 3.5 hours, caught on fire three times, burnt two fingers and had to be pried out of the case after using a damn heat gun!

Sincerely;

_Hacksaw


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[DerekTheGreat]

Not sure how the electrical system fully chooches in a "modern" car but I'm going to assume it's fairly similar to the old stuff.

I'd check it's voltage output first. Start the bastard, go find the battery and whip out a voltmeter to see what it's doing. Should be 13.9-14.7v or something like that. If it's any less than or higher than that, alternator is probably dicked buut, before you condemn it, Clean up all your connections. So, battery terminals to start. If you've got those shitty $3 ones in place of the factory stuff, no, just no. Those always leave you stranded when it's least convenient to be stranded. Solder on ones like what came from the factory or have them soldered on. Then clean up the connections on the alternator and the ground for the battery. Check again and see what you've got voltage wise. If no bueno, remove alternator, have it tested and then replace if defective. Those are my two pennies worth.

[Kodachrome Wolf]

I had a voltage regulator that was in the ‘97 before. Every so often the light would come on, then go out. Sometimes it would stay on for a bit, and sometimes it was only a few seconds. I swapped it for a replacement and it’s been fine since.

The only cars that get a bit more unique with the charging system are the ‘03+ cars, since they actually controlled by the PCM. The ‘02- cars just use the setup we’re used to with the sense wire, battery light wire, and for ‘97-, a stator wire.

IIRC, 1998 models are unique because they all used the 6G alternator, while in 1999 and on civilian cars got the 4G alternator and the police cars kept the 6G alternator (the 6G was replaced with a higher output Mitshubishi model, but I forget the change over year, but it’s outside of the scope for use here).