Trailer hitch wiring & engine overheating

[Capn Frank]

I recently developed 2 problems with my 2001 Pathfinder SE (62K miles):

1. When I connect my boat trailer lights to the hitch connector, the trailer lights do not work. I connected the trailer to another vehicle and the lights worked. I tested the 4 little ports on the connector with a volt meter and could not find any voltage. These things are sometimes wired into the rear lights of cars, so if it doesn't work, I would expect the truck rear lights to not work as well. The lights/brake lights all work on the truck.Does anyone know where to look / what to check? This is a dealership installed Nissan hitch - I had it installed when I bought the truck new.

2. I towed the boat anyway (no lights) .. and the truck overheated. Then I unhooked the trailer, waited a few hours, drove it again, and now it overheats with regular driving. Could this be a stuck thermostat? If I turn the heat on, the engine temp comes down...

[NISTECH]

#1 issue check for ground on the plug the exposed one is your ground. If it is infact a factory harness, there is a small box attached up near the L/H side behind the bumper aboove the EVAP canister, that is the convertor. see if its there, if so it is a factory harness. The way its connected is a jumper connector is wired to each tail light, you can undo the 2 bolts that hold you tail light in and pull it out, pull the rubber boot from the body and the connectors should pull out through he whole. you should be able to tell if it is a jumper harness or not as it will be like a Y in the harness. Note you may not be able to pull both sides of the Y through the whole but should be able to tell by looking at it. If you have a digital camera and can take a picture and post it of the connector behind the tail light I can tell you instantly weather its the trailer harness hooked up or not. If you find it is connected properly that little box I mentioned earlier might be fried.

#2 issue. Its hard to say for sure if its T-stat or not. Have you checked your coolant level? You could also have a restriction in flow in the radiator. If the level is good ,throwing a t-stat in wouldnt hurt as its a cheap first start and a good preventative measure. If after replacing it you still have an over heat issue I would suspect the radiator as the problem. Before you do anything though make sure the clutch fan is working correctly and there is no debris in front of the radiator cooling fins.