My new-to-me '78s headlights only work with the high beams on - the low beams don't work at all. I've replaced a bulb, but it didn't fix it. Is this a common problem in these trucks?

TM

 

check or replace the Dimmer switch on the floor.

Check for power to the headlights on the wire, at the headlight switch.

 

Ditto, Dimmer switch.

 

OK, thanks. I'll check it out later tonight.

TM

 

Hey guys, my truck is kind of like this but it seems like a heat sink problem, on low's my lights will work all night, but after a few min on high the lights will flicker on and off. If I turn it back to lows doesn't necessarily make the problem go away, that only happens if I open the vent under the dash on the kick panel and blow cool air under the dash, the problem will go away again. I am thinking the light switch in the dash is bad, what's your opinions?
Chris

 

No heat sink.
The breaker is built into the switch ,that's why the flcikering lights & that's why the cool air helps it out.

GM used a relay system, & this is something I encourage users to do to their trucks.
Run the Lights off of relays.

http://faq.auto.light.tripod.com/headlamp-harness.html

 

The breaker in the light switch is bad. You can replace the light switch or do like Dennis says and use relays. The relay system is worth the effort if you do it right. There are tech papers and many posts here on relays for headlights.

 

ok next question. the lighting is at best marginal on this truck. What is the best option for upgrade? And as soon as I get a chance I will do a search on this forum for this but I am just wondering who has upgraded the lights and is happy with that upgrade?
Chris

 

When you say lighting is marginal please be more specific.

headlights,interior lights,marker lights ?

I suggest to do the modification.
It costs about $25.00 and takes an afternoon to do.

Just make sure you get the good BOSCH relays and the new Fuse (Blade fuse) wiring for the job.
I will post 2 more sites than the one above.

 

http://www.danielsternlighting.com/

 

I am talking about the headlights. I dislike the yellowish glow and the fact that they don't seem to light as well as my 94. I know it is 20+ years older, and that makes it hard to see well.
Chris

 

I'm going to do the relay conversion as soon as I get caught up. With that and say sylvania halogen seal beams you should have a big improvement.

 

I use the Xtra Vision headlights in my 77. They put alot more light on the road. They are about $13 each at AutoZone. I think that Sylvania makes them.
Jimmy

 

I like the GE bulbs myself