240 Battery light on after shut down (remains on after Key removal)

240keith · 07-30-2021, 11:47 PM

Hey All

1985 240 DL

Ive got a new problem that seems kind of unique....

The battery / charging light comes on after the car is shut off, and the key is removed.

It seems to be charging ok (approx 15v) while driving via an accessory volt gauge wired as the factory would have.

I plan to check and clean grounds, and can grab an actual voltage reading.

The car has an "upgraded 100 amp alternator" (denso, I believe - I installed it a few year ago)

What are my steps to correct this, and how do I keep it from draining the battery after I walk away (battery is currently disconnected)

Thanks!!

dl242gt · 07-31-2021, 11:01 AM

On the denso alternators when the regulator fails this is the kind of weird problem that can happen. I'd double check that it's got good wire connections. Especially the ground from the alternator case to the block. If that is all good then I'd try a new regulator. That's a good time to check/replace the brushes while you are doing the regulator.

alschnertz · 07-31-2021, 11:06 AM

I've heard alternator diode failure can cause those symptoms.

07-31-2021, 11:01 AM	#2
dl242gt Old and boxy but good. Join Date: Jun 2002 Location: S NJ, a suburb of Phila.	On the denso alternators when the regulator fails this is the kind of weird problem that can happen. I'd double check that it's got good wire connections. Especially the ground from the alternator case to the block. If that is all good then I'd try a new regulator. That's a good time to check/replace the brushes while you are doing the regulator. __________________ Dave, 1982 242 turbo. 338k miles. MVP coilovers and 3" exhaust. Flowed 405 with a V15. Cossie turbine housing with upgraded compressor housing. 90+, IPD remote oil filter. Some other goodness, too. Been lots of fun over 25 years. Restored in 2k. Now ready for a 2nd restoration. 1993 245 Classic, 440k miles, enem V15. IPD bars and chassis braces. Simons sport exhaust from Scandix. sbabbs ezk chip. Been a good road warrior. Genuine Volvo rebuilt leaky M47.

07-31-2021, 11:06 AM	#3
alschnertz Enough already! Join Date: Oct 2009 Location: CT	I've heard alternator diode failure can cause those symptoms. __________________ Differences of opinions should be tolerated, but only if they're not too different. - Sharon Craig

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