Trailer tail lights

My Mack is a 2001, and has a fuse box under the hood in that same location....left side, near the steering column. Inside are fuses, breakers, relays, etc. for most of the lights. The other day, my trailer lights didn't come on when I flipped the switch...had to get out, pop the hood, open that fuse box, and wiggle the relay. Apparently it wasn't making good contact.

There SHOULD be a diagram telling what each fuse/breaker/relay does. Check both under the hood AND interior fuse boxes, because there are likely fuses and relays in BOTH places that can affect the lights.

If you don't see any problems with the relays, breakers, or fuses in either box, on my Mack, the trailer plug wires are terminated at a terminal block under the hood by the coolant reservoir...left side, near the fire wall. It'll just be a strip with a bunch of wires running to it. That's the OTHER end of the wires that run back to the plug at the rear of the cab where you plug the tractor end of the pigtail into. Get a test light and see if the tail light wire is getting power to there. If it is, then unplug the pigtail at the back of the cab and see if you're getting power to the tail light pin in the receptacle. If you are, plug the pigtail back in and test the tail light pin on the trailer end of the pigtail.

I'm going to guess, if the problem started happening after the OP ripped the plug out of the trailer turning too sharp, the problem is in one of the receptacles or the pigtail....just got to start where there is power, and see where it is lost.

If fuses are blowing, start by disconnecting the pigtail from the back of the cab. Do you still blow fuses? If so, check the wiring at that receptacle. If not, plug in the pigtail at the tractor side, but NOT the trailer. Do you have power through the cable? Did the fuse blow? If not, plug into the trailer. Do the lights come on? If not, and you had power through the cable, then the issue is on the trailer. If the fuse blew when you plugged into the trailer, check the receptacle wiring...doesn't take much, just a single errant strand of copper making contact where it ought not be.

Electrical problems are a S-O-B....

 

Volvo started equipping them with an external fuse and relay center on model year 2010 and newer. The external box above the steering column is not applicable to your 2000 unit.

Check the fuses and relays in the FRC (fuse relay center) that's under the top cover above your radio. The trailer lighting should be labeled on the sticker on the back side of the cover.

 

I had same prob on my 770. It was the pigtail.

 

Did you wiggle the pigtail to see if the light would come on?