'94 GMC Sierra K2500 Headlights Not Working Right

Same truck ('94 K2500, (7.4L) 454 V8.

Was trying to drive it last night, and about 2 minutes in, I began to smell a faint odor of something getting hot.

A couple minutes later, the headlights started to go out, and that faint odor of something hot started smelling like burning electronics, so I had to turn around and drive back — in the dark with no lights — to where I came from (it was lucky I was with someone so I could follow their car back, or else I wouldn't have been able to see). I found that wiggling the switch would make them flicker a bit, but they wouldn't stay on.

I haven't had a chance to look at it yet, so to get things started, I'll ask concisely and succinctly:

What happened and why, and how do I fix it?

c

Sounds like you have an electrical short that is overloading the switch and causing the plastic to melt. Definitely pull the switch as it will need replacing, and find the short before you have a fire.

GrimsterGMC said:

Sounds like you have an electrical short that is overloading the switch and causing the plastic to melt. Definitely pull the switch as it will need replacing, and find the short before you have a fire.

Click to expand...

Very sound advice!

I will order a new switch and either have a look at the wiring myself, or take it to the mechanic (it's due for a tune up anyway, and unfortunately, I'm not equipped, nor do I have much time to do that myself).

c

From what I recollect about a similar thread I read on here, it sounds like the thermal breaker for the headlights is doing it's job. Look into the switch in the dash, but also the highbeam/lowbeam switch in the steering column. Those things get crusty over time, circuit generates heat and eventually magic smoke can be released once the circuit reaches peak ecstasy.

I had the same problem with my '88 k 3500 years ago, I found that power feed from the switch had melted the connector that was behind the glove box after a bit of searching.

I have yet to actually check any of the wiring, but I'd like to know what, if any parts I should get other than the switch.

Connectors? Wiring harnesses? Fuses?

Thank you!

c

cc333 said:

I have yet to actually check any of the wiring, but I'd like to know what, if any parts I should get other than the switch.

Connectors? Wiring harnesses? Fuses?

Thank you!

c

Click to expand...

The only way to tell what parts that you will need is to take it apart and start looking for problems.

Fixed!

Apparently all the wiring is OK, and it was the switch.

With the help of a friend, I opened up the switch and looked at the contacts. One of them – the main headlight circuit – looked visibly burned. Some quick trial and error determined that the contact was still intact, but was caked with dirty, burnt dielectric grease, so after cleaning it up with some mineral spirits, the headlights started working again!

As I was doing some research, I came across a listing at LMC Truck for a retrofit kit that rewires the headlights so that they draw power directly from the battery instead of through the switch. It costs about $26 for the wiring harnesses and another $15 for the relays. I'm sure I could do it myself for less, but the kit is appealing because it's easier and quicker to install.

Thoughts?

Also, I have a new switch on order, so I can have it ready to swap in if/when the existing switch fails again.

c