2005 gmc 2500 trailer light problem

[silveradosid]

replaced wiring at the back of the truck , all lights function on the truck but when i hook up the trailer and step on the brake pedal no right hand brake light, turn of right signal and light flashes. all marker lights work and the electric brakes work. when i turn on left signal both signals flash on the trailer but the truck still functions normally. i tested plug on the truck and it does put power to both signals when the left signal is on. traced all the wiring in truck and cant find a problem. could the signal switch be putting power to both trailer signals and the truck still function normally

[Formulabruce]

Did you replace the small harness from the truck main harness to the receiver unit? Usually a round 7 pin?   The truck uses separate brake and turn bulbs and the trailer can be a 1 bulb deal for this. There are some small plug in testers for your truck at parts stores which can speed up this process.

 The trailer. I use a power probe and power up each circuit at a time and check all of them to ground and make sure none are shorted. One I found the inverter in the TT was messed up and actually shorting the 12 volt side. Good luck !

[silveradosid]

yes replaced harness due to a short to marker lights trailer is good this problem is in the truck owner now tells me that sometimes when he puts the left signal on the 4 ways flash i told to buy a new signal switch will let you know if that fixes the problem