Head Light/Alternator Problem

[ed_in_pa]

I may have a short in my head lights but I'm not sure ('76 Corvette) . A couple months ago while driving a short distance at night my car started to stall so I pulled over, saw my battery gauge in the negative, I shut off my head lights and the car started to run fine again. I thought the problem was with my alternator not charging so I replaced my alternator and everything seemed fine. (I don't really drive it too much at night but on short trips it was OK.) This past weekend I took about a 1/2 hour ride when it was daylight and everything was fine. I returned in the evening and had my head lights on. As I was driving they got dimmer and dimmer and I noticed my battery gauge in the negative. When I shut the headlights off the battery gauge went to zero but not positive. After barely making it home I parked the car and figured the alternator was bad again. I exchanged the alternator today, installed it and started my car. It immediately went to positive and recharged the battery. My question has to do with the head lights. I still notice that when I turn the lights on the battery gauge goes to the negative, is this normal, to a lesser degree, I also notice the gauge going to negative when I use the electric windows. Thanks for any suggestions or help.

 

[Ol Blue]

ed_in_pa

I haven't had that exact problem, but I have had the headlights begin to cycle off and on. It was a bad dimmer switch. Cheap fix.
Ol Blue

 

[ed_in_pa]

Just an update. I took it for a 10 minute ride to a restaurant for take out. It was dusk, so I had the headlights on. When I was just about there it running rough and almost stalling. I shut the head lights off. Also, the turn signals stopped working. The battery gauge was reading negative to 0 most of the time. As I was sitting outside waiting it really started running rough so I shut it off. You guessed it wouldn't start again. I was able to get a jump and made it back home without my headlights on. I noticed the turn signals were still not working and the battery gauge was reading about zero. I would think it would be charging. Did I fry another alternator? Any thoughts out there?

 

[ed_in_pa]

Any chance this could be the battery, I'm not positive but I thought the previous owner replaced it within the last couple years.

 

[curtis]

your battery has an internal short or bad cell causing your alternator to overwork and burn up. the battery has no reserve if one cell is bad and will never charge up properly. Happened to me like that. Nothing electrical worked wortha d____. Put in a 1000 cranking amp battery and 80 amp alternator and problems gone.

 

[ed_in_pa]

Thanks for the info, so what your saying is I now have to replace the alternator for a third time, is there any chance a new battery will solve the problem without replacing the alternator.

 

[curtis]

check your alternator with a voltmeter. measure battery voltage with engine turned off. start engine and measure voltage again. If it is higher than alternator is charging. If voltage is lower it is not charging. Your local Advance Auto can check it out and your battery. They usually do this around here for free. Just be sure your battery is fully charged when you test it or when installing a new one.

 

[ed_in_pa]

Curtis, thanks for the suggestion about the battery and alternator. I replaced the battery with one that has 825 cranking amps and I had my alternator refitted to put out almost 100 amps. I've ran the engine with lights on, the radio on, and putting the windows up and down and the battery gauge never went negative. As an added bonus the battery was replaced for free because the previous owner had bought it in Jan, 03 and it was still under warranty.

 

[curtis]

sounds like yor problem is solved!

 

[SR'71]

Ed ... I see your prob is fixed. I'm not 1 to rain on a parade ... but .. check your ground cable from the bat. to the eng. block. Red lead on the Bat - post, black lead on a CLEAN METAL part of the block. Start. You should read in the millivolt range. Greater than the millivolt range = you have a bad cable or the ground cable is not making good contact or the eng blk ground needs help.