I have a 1996 chevy tahoe that I use for towing. This spring I hooked up to a trailer and found that all of the lights will dimly flash with the turn signals. I checked the trailer ground and it was fine. I then hooked up to two more trailers with the same result. I then realized that, on my tahoe, that the turn signal opposite the one I was using was also dimly flashing. I checked the wire connections and grounds to both rear lights and they are fine. Any suggestions on where to go from here? Thanks.
This definitely sounds like a ground problem but it doesn't have to be where a wire is bolted to the body. Suspect a corroded or stretched contact in one of the light sockets. One way to verify that is by removing other bulbs. What happens is the current going through a bulb with two filaments, (brake / signal and tail light), goes through the brake light filament, can't get to ground, so it goes to the tail light filament, and once on that circuit it goes over to the tail light on the other side, through that filament, then to ground. By removing the left bulb for example, the right one will go off completely.
Once you have all the bulbs removed, put one at a time back in until you identify the one that doesn't work by itself.
A more difficult way to diagnose this is to measure the voltage on the grounds of the bulbs themselves. That can be hard to access with the newer plastic base bulbs. It was much easier with the older brass base bulbs.