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I fired up my truck last night in the garage because it hadn't been run in a while. While idling I decided to test the lights. I noticed the driver's side light is now very very dim and the high beam isn't working. The right side light is nice and bright and working fine. The lights were both working the last time I tried them. They were never seriously bright but were much brighter than the driver's side is now. Seems as if the right side is getting most of the juice. Is this an electrical problem, or is the headlight itself on its way out?

Sounds like a grounding issue! Check the ground wire on that side!

I vote for a grounding/electrical issue as well. Generally these headlamps filaments blow entirley. I have never seen one die a slow death.

I agree with Ken and David

It's the ground

Agreed-poor ground.
Gary

We actually found where the douglas connector had grounded out - the brass ferule had pushed the rubber grommet inside too far towards the tip exposing a little of the terminal. It was just enough to make contact which grounded to the shell which grounded to the retainer to ground. We only noticed it because we saw a little arc mark on the shell.

Will this ground wire issue be within the headllight bucket, or is it a wire on the ooutside say under the hood someplace? I have not taken my headlights apart(other than to remove the outer ring for painting) so am not sure which wire to look for.

Nick,

It could be either. I would try this. Disconnect your headlight harness at the trouble side. Run a jumper to the bulb connections, positive and a ground, and see if the light gets bright. If it does then the trouble is the cab ground or harness someplace. Clean and inspect your connections to that lamp well also. Could be some minor corrosion somewhere?

We bought a front harness from Sid Beck and added a dedicated ground wire to the harness, that way we had no question on where the ground pick up was. Get a tube of di-electric grease and lube every connection after you clean them.

The headlight harness has a dedicated ground wire, terminates at the inner fender splash shield on both left & right sides.

That's where we used a grounding bolt with 2 star washers to make the connection right there on the fender guard.

I removed my headlight ground wire today, and cleaned up the bolt and the connecting loop on the ground wire. Put all back together but no luck. Still having the same problem. I tried to unplug the douglas connectors to check inside them but they are rusted shut, can't budge them open. Will try again tomorrow.

If the ground isn't an issue, most likely the sealed beam has an internal problem. Probably needs a replacement.

It doesn't hurt to clean up your grounds... It could be the lamp its self, or it could be your wiring. You need to get the connectors apart and put a volt meter on them to see if you are getting the correct voltage. You may have to chase the wires to find where the voltage drop is. Hunting down lighting issues can be a headache but in the end once you find the problem you will be a very happy person.