1989 240 Battery Drain Troubleshooting

Stitch333 · Post by **Stitch333** » 29 Jul 2019, 13:16

Hello Forum!
My mechanic and I are going through a 1989 240 and I am sussing out a battery drain issue currently.
When started and running, the battery terminals read 12.2V...
As I do research and start drilling down I noticed something and wanted an expert opinion:
What voltages-Amps should I be reading at the fuse block?
With key in and on, what voltage should I be reading at the alternator small red wire?

Apologies if this has been discussed...a link to threads going over this would be great!

Cheers and thanks!

EDIT: with the key on second pos, car not running...Im getting 11V at the small red lead off the alternator.
Is this the voltage reg on the alternator gone bad?

93Regina · Post by **93Regina** » 31 Jul 2019, 11:24

Make sure alternator is grounded

Stitch333 · Post by **Stitch333** » 31 Jul 2019, 13:36

Thanks for the response!
It's def grounded.

lummert · Post by **lummert** » 01 Aug 2019, 19:05

Have you checked the voltage at the battery with engine running using a VOM? IIRC the small red wire should be connecting to the battery light on the instrument cluster. Is the battery light functioning?

Stitch333 · Post by **Stitch333** » 12 Aug 2019, 11:28

Just a follow up: replaced the voltage regulator (the brushes were nubs)...
now min voltage at small red wire in key pos 2 not running, and 14.5 at the battery when fired up.
Seems it was the voltage regulator that was the culprit...

Cheers!