Reese Neis

So the GEN light came on in my 70 cutlass any ideas as to why and I’ve already checked voltage

oldcutlass

Gen light usually means its not charging. What voltage are you reading at the battery with the engine running? Should be around 14ish.

matt69olds

Unplug the regulator connector. If the light goes out, chances are the regulator is defective or the charging system isn’t charging. How did you check the charging system to determine if it is charging?

The charge light has ignition power on one side of the bulb all the time. The regulator supplies power on the other side of the bulb when the engine is running. Power to both of the bulb contacts, the bulb won’t light. If the charging system fails, or the engine stops, the regulator supplies a ground to the bulb, causing it to illuminate.

oldcutlass

The light gets its power on the engine side from terminal 4 on the regulator, so yes unplugging it will make the light go out but not prove anything.

matt69olds

I suggested unplugging the regulator to verify the brown wire isn’t grounded somewhere else. If unplugging the regulator causes the light to go out, then for whatever reason the regulator is supplying the ground to the bulb.


Part of through troubleshooting is finding out how things work the way they do, not just why.


I worked with a guy years ago that was convinced the used car he recently bought had head gasket issues. The hot light was on whenever he started the car. Turns out the previous owner recently replaced a valve cover gasket, he pinched the warning lamp wire under the cover. It took a little while for the insulation to wear thru and ground out. The guy wasn’t very automotive savvy, engines don’t instantly overheat. If the car sits for hours, and the temp light comes on the instant you start the engine, that should have been the first clue the warning lamp was useless!