I have an 03 Ranger 4x4 xlt 4.0. The left headlight went out 2 days ago. I replaced both lamps and the left light is still out but only the low beam (high beam works fine) I've checked all the fuses and they're good. I can't find any relays directly associated with the headlights and after searching the interwebs I'm beginning to think that my GEM is failing.....
Thoughts?

 

Under hood fuse box
Lt headlight low beam fuse 38 - 10 amp
Rt headlight low beam fuse 42 - 10 amp

 

Have you checked the wiring around the headlight, especially the ground.

Connectors go bad !

 

Those were the first things that I checked. Both in good shape.

 

The wire from the output side of fuse goes straight to the headlight, so problem is between fuse and light.

like Scrambler82 said, most likely problem is connector or broken wire right at the connector .

 

Marcusc,
I don't know all in's and out's of the electrical system as some of the members do and I appreciate them but do a quick check at the Light Connector.
Pull the connector, using a Volt/Ohm Meter, which I think you said you were going to buy anyway, check for the ground wire connection to the body of the vehicle.
Then turn on the headlights in Low beam mode and check to see if there is 12 volts coming in to the Headlight; after that do the same for high beams.
We need to establish what is working at the head light and what isn't.

After that if you find no power in the wires you will need to trace them back to the relay that controls them.
Also one of the most important words is the ground, if it isn't connected electrically to the body you need to establish a good ground to the light connector.

Since it is just the low beams, left side, you know where to start.

NEXT..., if the connector is corroded, wires broken, or just thing are getting old, and you intend to keep this truck for a while, buy a Heavy Duty Headlight Harness, if you can't build one. Make sure you buy or build a harness that fits your needs today and tomorrow, make sure the new harness will support a 100watt headlight bulb system.
Sometimes you need to do some cutting of the harness and soldering, but most of the time the replacement harness uses the existing harness for the switching.
Then there is the new Ground... make sure that the ground in the new harness returns directly to the battery negative terminal, not to the body, AND the gauge of the ground wire is at least one gauge larger than the supply wire.

If you decide to build a harness and need an assist, I am available and there are a number of others on this site that I know are more than capable of giving you good advice.

Good Luck and IF you decide to check ou tteh Headlight Connectors, POST your results of your Headlight Test, I'm very interested.

Ltr