I have my 97 T100 truck wired for a trailer. It has one socket that hooks up to the truck to run the electric brakes and the all the lights. It was installed professionally. It used to work fine, but slowly one of the taillights on the trailer got dim. Then only one turn signal worked. Then they eventually went out. Alll the running lights on the trailer still work, I can turn on the lights on the truck and the trailer tailights will light, but no turn signals or brake lights. Electric brakes work too. I took the trailer and truck to a trailer place to have it checked and they said the trailer is fine. Also initially said that the truck wiring socket was fine too, but sort of questioned their testing tool. Now they are telling me that on Toyota trucks that have been wired for tow packages from the dealer have something called a "converter" and that this is probably bad. Any one know if this is feasible? I checked all the fuses, including all the extra inline ones that seem to be for the trailer and all seem fine. Anyone know what this converter is and how do I know if it's bad? Thanks.

 

Without the trailer connected check the plug at the back of the truck. You can use a test light style tester, where you clip one end to ground then it lights up when probing the connector. Have some else in the cab turning on the lights, turn signals, etc. Even though you have running lights on the trailer I think you have a bad ground between the trailer and the truck.

I had a 4th gen 4Runner and rented a U-Haul trailer. The U-Haul dealer had to run a ground wire from the trailer side to the 4Runner's trailer connector to get everything to work. It was just not a good enough ground via the receiver hitch.

Good Luck

 

same trouble on my t100 with a bad ground.

 

Ok, it was not a bad ground it did indeed end up being this converter. The trailer place replaced the converter and the problem was solved.

 

I am glad it is working. I hope it wasn't too big of a hit in wallet.