So I've noticed a few times when I get back out to my truck from going in the store that my fog lights will be on randomly. Switch off, no headlights. Just fog lights. Any ideas what the cause could be?

Need more info about your truck.  Is your truck a standard 2 bulb headlight system or a 4 bulb Quad headlight system?  Do you have factory daytime running lights (Canadian truck)?  And last, has your headlight / fog light system been modified?

 

Also, what year and model is  your truck?

 

- John

 

It's a 2000 Ram 2500 single cab long box. Cummins with a nv4500. Standard 2 bulb headlights. Not a Canadian truck. And the only mod to the fog lights would be the wires were cut when the bumper was removed and soldered back together.

Thanks for the information.

 

The wiring diagram below is from the 2002 FSM.  I don't know if it applies to your 2000 year model truck.

 

If by chance the wiring diagram is the same, then I would check the condition of the fog light wires that were cut and repaired.  The 15 amp Fuse G in the PDC supplies battery voltage directly to the fog light.  If a grounding wire leaving either fog light were unintentionally grounded prior to the fog light relay, then the fog lights would come on.

 

- John

 

Edited May 19, 2024May 19 by Tractorman

Could be a bad switch or the ground side of the bulb lead is shorting to ground.