Electrical issue

[ColoradoSteve]

Just got the '83 up and running after a long, cold winter. Replaced the battery, it was not holding a charge. Here's the problem: the alternator ( about a year old) produces a steady 12.1 -12.8 v until I turn on the headlights, then my voltage immediately drops to 11, doesn't go any lower. It will do this if I turn on the foglamps or the headlights or both. Doesn't do it just for the parking lights. I have checked the headlight switch ( also new ) and the belt tension on the alternator and these are fine. I guess my next move is to clean all the contacts to the lights, anyone have any ideas what's wrong?

[fmartenies]

Voltage doesn't run anything, watts do. Your alternator shows correct voltage at a lower load if the regulator in it is working, but that is all a volt test does. If your windings are bad you will not produce enough watts to meet the draw everything in the car requires. You need to check that you are producing x watts at y RPM's, but I don't have the exact numbers for the car. Hopefully somebody else puts them out there.

Voltage = water pressure, Wattage = the amount of water coming out of the pipe.

[krystar]

the issue could also be the grounding cable. make sure it has a good solid connection to the body metal. take off the bolt and wire brush it clean to remove any corrossion/funkiness

[chip18]

Check the bushings in the Alternator the one in 8.5 N/A was incredibly worn, replaced it and it was all ok again.

[bazar01]

Originally Posted by ColoradoSteve

Just got the '83 up and running after a long, cold winter. Replaced the battery, it was not holding a charge. Here's the problem: the alternator ( about a year old) produces a steady 12.1 -12.8 v until I turn on the headlights, then my voltage immediately drops to 11, doesn't go any lower. It will do this if I turn on the foglamps or the headlights or both. Doesn't do it just for the parking lights. I have checked the headlight switch ( also new ) and the belt tension on the alternator and these are fine. I guess my next move is to clean all the contacts to the lights, anyone have any ideas what's wrong?

With the car running in idle all loads off, 12.8 V is too low. You should get at least 13.5V with no load. With load, it should drop to 13V. Your alternator is not working. Have your aternator tested at a nearby auto parts store.

[AKCJ]

I agree with bazar - below 13 is too low if the vehicle is running. The brushes (not bushings) in the alt are probably worn out. You can just put in new brushes for cheap or do a better rebuild like clean it up and put in new bearings while you're at it. Or, pop for a new alt.

I would also guess that there's a good chance the battery is toast from not being charged.

Tip - think of the battery as full at 13.5 volts and dead at 10.5 volts.

[ColoradoSteve]

Thanks for the replies , guys. I checked all connections and everything seems fine. I will have the alternator tested , I thought it was OK because I replaced the thing less than 5k ago. Weird.