Hey all, I feel like this is a never ending set of problems with my truck (but I still love it!). Got most of the other issues ironed out, so I can finally get to the instrument cluster. I've got a 02 F150 Supercrew 5.4L. All of the lights inside and outside of the truck are working, the radio is working, and all of the warning lights on the dash are working. However, the instrument cluster illumination is not working. I checked the fuses, which all look good, so I suspect that it's the dimmer switch. I've got it pulled out, but I can't seem to find a wiring diagram for it, so I'm not sure what to test or what to look for. Any suggestions would be greatly appreciated!

 

Oh, I forgot to mention, I pulled the bulbs on the cluster, and they all work fine too.

 

No one's got any ideas? This problem limits my driving at night, since I can't see my speed.

 

Do you have a multimeter and do you know how to use it?

 

Thanks for the reply projectSHO89! Yes and yes. As I mentioned, I did test the fuse for the instrument cluster (can't remember the number right now) and it was good. I just can't find a wiring diagram for the dimmer harness, so I'm not sure which lines to test.

 

At the back of the light switch, check for power at the DK BL/White wire of the 6-pin connector with the switch set to either PARK or HEADLIGHT. If missing, troubleshoot feed from CJB F18.

If input power to the dimmer circuit was present (above), check output of dimmer on the LT BL/RD wire (same connector) while running the dimmer control back and forth. A properly operating dimmer should cause that voltage to rise and fall with the dimmer control.

If the input was good but there is no output, the dimmer is probably bad.

 

Got it. Confirmed that it's a bad dimmer, thanks!

 

Finally got the new dimmer. Installed it tonight and all the lights are finally back on. Thanks again for all your help!