I just got my truck back on the road after sitting in my garage for a year. I had to jump it to get it started and when I did it wouldn't idle properly on it's own. It would idle and rev just fine when jumped. The battery was completely shot. I was testing out my lights while it was idling and both of my headlights blew out when I tried the high beams as with a few other random external lights. Everything worked fine prior to being parked. I bought a new battery for it along with all new lights. It starts and runs fine but now it has issues burning out headlights only when I select high beams. Also my reverse lights don't work. I do not have an ohm meter to check voltage but I do have a test light. I checked all my fuses and they are good. I'm getting power to both of my headlights and my dimmer switch looks fine. Is there a chance that a bad dimmer switch could cause this? Thanks.

-Destin

 

B/U lights ? What year truck ?

Dimmer switches are prone to corrode and cause numerous problems

Headlight switches usually go faulty slowly

 

The frame is a 76 f250 4X4 with a 78 f150 body on it. Is there any way to test the dimmer switch? Ohm meter?

-Destin

 

Do you mean the headlights burn out or the fuse does? Either way, the high beam switch is likely shorted and needs replaced.

The backup lights share a circuit with the windshield washer pump. If the fuse is okay, you will want to visually inspect the reverse light sockets for corrosion. If all looks okay, the issue lies with the neutral safety/backup light switch located on the left side of the automatic c5 and c6 tranny. Use a drill bit to readjust it before buying a replacement switch.

 

If all the bove checks out ok, unplug the nuetral/reverse wiring harness at the top of the firewall near the center (it's the harness with 4 wires in it) and use a jumper across the pins to test for reverse lights, if the light work your switch is either out of adjustment or has gone bad.

 

I put a new dimmer switch in and my headlights are good to go however my back up lights still don't work. I'll check that plug out later and see what comes up. Thanks for everyones input. I'll snap some pics and post em up in the picture thread here soon.

-Destin

 

Update:

I was on my way to the car wash to clean up the underside a little. I made it to the end of the street and my headlights burned out. They lasted longer than before and seemed to be good earlier today however I only had em on during the day for less than a minute to test em. Could I have a bad alternator or a bad voltage regulator? Is the voltage regulator internal or is it external somewhere? I have a 76 high boy with a 78 body on it.

-Destin

 

Your regulator is on the right side inner fender, about a foot to the left of the Battery, Try reading your voltage with a meter with the truck running and at a high Idle . Should read 13.5 to 14.5 volts. If you have a spare headlight swith you could try swapping it out. I've had a few problems caused by the main switch, not the same type as you're having but troublesome to find as well. The headlight wiring runs down the left inner fender to the Rad support and then across to the right headlight, is there any signs of wear or rub marks on the wiring?? Good luck with it.