We have a 2010 express bus at our shop. The headlights go on and off randomly. Fuses are fine, switch is fine, we are fairly certain we have a relay problem. We can not find this relay anywhere, the book doesn't show a relay, however the under the hood fuse box shows in a section labeled "Circuit board relay (not shown)" a low beam relay. Does anyone have experience with these and know where the relay is located?

 

Click on the link 'GM Upfitter' in my signature. Browse Light Trucks, Look for your Year, Select the Electrical Schematics link for your Van.

 

PCB relays are non-replaceable (likely solid state devices), and your problem lies elsewhere. Check for loose connections, broken wires, bad switches etc.

 

forward lighting relays are in the UHFB...your problem sounds like a loose ground wire though...there are some just inside the drivers kick panel and then some on both the drivers front frame and drivers side of the engine block..