1996 3500 No Headlights

[Hank Themak]

Have 1996 Chevy Cheyenne K3500 with 350 engine.

Problem: No headlights which were working fine and just stopped working.  Checked and replaced fuze and one sealed beam but still not working.

Just not getting power to both sealed beams.  Hi-Lo dimmer switch works as dash indicator light does work.

Wiring diagram shows a diode that is located in the under hood fuze bock.  Do they fail?

Wiring diagram also shows a couple of relays but can't locate them under the hood.  Not located in the under hood fuze and relay block.  Where are they located.

What else should I check?

[Jsdirt]

A '96 could be controlled by the Body Control Module (BCM) - I know for sure the 1500's are, but not sure about the 3500. That throws a million other variables into the mix. If you've got tiny little 22 gauge wires going to your switch, it's more than likely computer controlled. All the switch does is send an input to the computer.

 

Even still, there should be a relay in the underhood fuse box. 9 times out of 10, this is the cause of lack of lighting. 8 times out of 10, it's a failure of the magic box - either loss of powers or grounds to it, loss of inputs or outputs, or bad unit itself.

 

Make 100% sure you've lost power at the lights. Loss of ground will do the same (if they ground together, and not near the lights - chances of both grounds failing at the same time are slim).