There are no extra fuses for your trailer lights. If you have the towing package (and you do) the trailer lights run through your regular fuses (tail, brake, turn).
There are separate fuses for trailer signal lights in main fuse panel
The 2002 Chevrolet avalanche horn and trailer lights have different fuses. The fuses can be found in the fuse box. The location of the fuses can be found on the inside cover of the fuse box.
check fuses under the hood
Check your fuses and look for a dead-short on the tail light wire (probably brown).
The fuses in the 1989 Mercedes 300 control things like the lighting system, the door locks, the wipers, and the instrument gauges. The fuses also control the trunk latch and the turn lights and brake lights.
Check the four fuses that are behind the seat that support the boat trailer lights.
A short to ground causes all fuses to blow. If you have a trailer connecter then start there first.
Check your alternator it could be malfunctioning. Sometimes it gives you warnings like this.
Check that the wiring between the truck and the trailer are connected. Unplug them and then plug them in again. Also check the fuses under the dashboard (if it is a moving truck, there are also fuses under the hood) to be sure they are ok. Finally, check the bulbs in the lights.
Open the hood and look in the engine compartment. On the forward left side (as if you are looking forward from the steering wheel) there should be a fuse box. The cover should pry off with finger pressure. On the inside of the cover is a diagram of fuses. Look for a 15A fuse that says "Trailer running/clearance lights". Pull it out. If there is any discoloration or sign of burning, replace it. This should give you power to the trailer. If you have any other lights out on the trailer, check some of the other fuses. Turn/stop/ back up lights have fuses in this location.
Does it have trailer light wiring also? check that too.
Brake pedal switch, wiring, bulbs, bad trailer harness (if there), fuses...