Headlight/Electrical Issues

[Big69C20 Toy]

Hey all, on my recent trip out to MI from Cali, i ran into some electrical troubles.

In Eastern Colorado my low beams decided to go out, as they had done before intermittenly in years past. So i just dealt and drove on with the hi beams (sorry to all i passed with 130W blue xenons).

Anyways the truck drove on and was fine but i'd notice at times that my voltmeter would be seemingly dragged down, then kick back up to 14.7 or whatnot after a bit. That is until western michigan, my volts kept dropping and dropping until i didnt have enough juice to accurately fire my ignition system (man that sounded like heck)

Pulled off the highway and i had juice but not enough to fire up the truck, got a jump and proceeded to get a new Bus fuse for the headlights thinking that may be the problem, not so. I still had no low beams and my highs would keep draining the system, heck i dunno if it was them or the running lights or what exactly

So my question is what should i check out on this thing? It has a stock style alternator that is i dunno how old and with that 572 under there i thought the thing might be overheating or something too.Perhaps my voltage regulator (dunno what it even looks like) Driving the trucks with no lights has proven fine but i'm unsure.

Some direction/advice would be great. Thanks fellas.
Greg

[tom hand]

I am thinking the problem with you headlights is the dimmer switch. And maybe you alternator is not big enough to run those 130w bright lights continuously. Under normal use t shouldn't be a problem

[71GMC_3/4T]

Check your fan belt for glazing and check your pulleys on the alt to be sure they look like a V, not a U (caused by wear).
If all that looks good, shotgun the regulator, which, if still the old style, should be on the radiator support on the drivers side in the engine compartment. They go bad after time.

I had a '74 Monte Carlo that would drag the battery down when the heater was on high. The fan belt was glazed.

Good thing the highway patrol didn't pop ya for running on high beams! Glad you made it home okay.

[neonlarry]

It could be your alternator or battery going out, I would check them first. But my best guess is that you need to upgrade your electrical system, these old trucks weren't meant to handle all the new high powered stuff i.e. your 130W headlights, 900W stereo etc. Check out thisLINK for some info on upgrading your system.

[busterwivell]

I know this will sound stupid,but it happened to me once. Same deal, going on a rod run and it came time for headlights. My friend called me on the CB and told me turn on the lights. I told him they were. We pulled over and found the tail lights were on, but not the headlights. I put on the brights (4lights)and they worked but not the lows. Followed my friend in to the hotel with brights on. Next morning checked and found that after I finished putting my new aluminum manifold on the night before we left, I had not tightened up the ground cable! It was grounding through the bulbs. Two new bulbs and a tightened cable and all was well with the world again.

[Big69C20 Toy]

hmm i'll check the alt, and belts, but the belts are brand new, thought after that long mean trip it could be the case.
The switch is also an idea, i found before i had a loose wire causing that thing to not switch the hi/lo appropriately, i'll check it again. Thanks fellas.

By dimmer switch did you mean the hi/lo switch or my panel light switch? because my hi beam indicater often doesnt like to work.

Thanks all.

[Fred T]

Dimmer switch is the push button on the floor. I would check all the wiring connections and be sure of a good ground first.