Here is the scenario:

Only after the truck sits for several hours, when I turn on the low beam head-lights, only the parking light illuminate, no low beams.
The high beam head lights work fine.

The low beam heads remain non-functional until one of the following occur:
1) Truck warms up after several minute of driving
2) I hit a decent size pot-hole
3) I open the hood.

It would seem that I have a temperature related short that is brought on by the cold and goes away once the under-hood temps warm up... or until the engine compartment gets jarred around by encountering a pot hole or other abrupt road surface... or I open the hood.

The last one is the most peculiar.
On a cold morning, I have no low-beam until the instant I pull the hood latch.
Once the hood latch "pops" the hood open, the head lights come on.

Ive attempted several different processes to locate the short, but once the low beams come on, the problem does not re-occur until the truck sits for several more hours and cools.

Any "Bright" ideas or info would be greatly appreciated.

Thanks.
Rich

 

I currently have the same problem, except my low beams won't come on at all. When my truck was new I had the same problem and could get the low beams to come on after flicking the dimmer from low to high beams a few times. Pretty easy to replace the multi-function switch. This time replacing the switch didn't fix it, nor did a new headlight switch that I carry around as a spare. I was in Butte, MT with a trailer headed to Kalispell when the problem came up. I turned my adjustment screws way in and came back to TX using the high beams. Today I'll put it in the garage and start troubleshooting. If the dimmer switch trick won't work for you perhaps what I find will help you.

 

Yeah, the high/low beam switch (Turn signal) is known to get dirty contacts.
In my case, I dont think dirty contacts are the issue.

Thanks, keep me posted if you do find anything else.

 

Well, unlikely as it sounds the only problem with mine was both low beam filaments were burnt out at the same time But I chased all the wires, so here is how the circuit works. The lt sw powers the multifunction switch with a light green 16 gauge wire. Low beam power is a 16 gauge violet/wht tracer that goes to a black connector next to the steering column. From there it goes to a splice that is behind the left headlight and under the battery. It splits to each headlight. My guess is that is where your loose wire is. Each headlight has a separate ground so I do not believe that is the culprit. Hope that helps.

 

I too, had my suspicion that its something around the harness split under the battery.
I guess this weekend, I'll start digging around to see whats loose.

Thanks.

 

Sounds like a bad ground to me. Find the ground plug in your headlight socket and pigtail it to a good ground. It may not be a bad ground, but that's where I would start. Seems to me if you had a short, a fuse would pop.

 

Each headlight has an individual ground, guess you didn't read my whole post. If it was a ground problem then only one light would be giving him problems. Also, each light's plug share the ground so if it was bad the high beams wouldn't work either.

 

Actually I was responding to the original posters comments not yours. He asked for suggestions.

Mr. Daze. Sorry about that. I do hope you get your problem fixed. I did not see the last line where you stated that your high beams were operating. My apologies sir.

 

I just came out from under my hood and could not find any (obvious) loose connections.
I traced the main wiring loom to a split located near the drivers side battery box.
From there I continued to trace the wiring down to each head light.
I shook, twisted, gently pulled the wiring loom(s) as I progressed and that resulted in nothing.
The low beams still do not work when cold.
I checked the 40A fuse under the hood and switched it with another 40A fuse just to check... still no low beams.
I crawled under the dash and checked the wiring from the switch and steering column area to the firewall for anything loose... nothing.
As of this post, I still have not found any loose connections.
I am currently out of time for now.
I will continue to investigate the grounds later this weekend.
Thanks all. No need to apologize for anything.
I appreciate all input, ideas and suggestions.

Rich

 

Rich,

Just a thought for diagnosis. I am assuming you keep your tuck out side. You could try putting a electric heater inside the cab to just heat up that area. It seems if the cab wee kept warm and the lows still do not work, your issue would be in the engine compartment.

I was also thinking you could take a utility light and warm different areas of the wire run to see if you could isolate it further?

Isn't electricity fun!!!

Do you have an electrical schematic for this circuit for your truck you could post?

 

It would involve taking the battery out again but I think I'd tap into the Violet/wht wire under the dash and run a new wire to the violet/wht wire just before the splice. I had to do that to power the tail lights and bed marker lights on mine. Somewhere in the bundle under the hood is a break and bypassing it was a lot easier than unwrapping all those bundles.

 

how about a headlight relay that is going bad??

Just food for thought.

 

The headlight switches are notorious for going bad. Pull it out and check for melted plug?
Just an Idea. Unless you have the fix for adding relays/wiring harness.

 

I was kind of thinking the same thing they are real easy and quick to swap around to see if the problem moves.

 

There are no relays for the headlights in the stock wiring.