Left Turn Signals Not Working When Hooking Up Utility Trailer To Truck

Updated 02/04/2020 | Published 09/28/2011

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4-Pole Trailer End Connector

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$7.47

Hook Probe Circuit Tester

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$13.68

Question:

i just hooked up my utilty trailer to my truck. when i put my right signel on it works but when i put my left signel on even the signel on my truck wont blink. very puzzled

asked by: Perry B

Expert Reply:

Sounds like it is a ground problem. I would start with checking the ground of the left tail light of your utility trailer to make sure it is making a good ground.

The tail light assembly is grounded to the trailer by either a separate ground wire to the frame or by the bolts of the tail light assembly being attached to the frame of the trailer. You will want to make sure the tail light assembly is fastened to the metal trailer frame securely and making a good ground. If it has the ground wire instead, make sure the wire is attached to clean metal on the trailer frame.

The next ground to check is the connector on the trailer. It should have a ground wire from the connector attached to a clean surface on the trailer frame.

The last ground to check is the connector on the tow vehicle. It should have a ground wire attached to a good clean ground on the vehicle.

I would also recommend using a circuit tester like the part # PTW2993 and test the wire for the left turn signal going into both connectors and coming out to find out if the connectors are bad.

I am including a link to a FAQ page on trailer wiring.

expert reply by: Jeff D

Steve M.

2/2/2020

Im having issues with the lights and turn signal and brake lights with my pop up..I have bought another pop up and everything works fine but the other one will just have a right taillight work but nothing else. I dont have the popup on my hitch when trying the lights..any suggestions?

Jason S.

2/4/2020

If I understand the situation correctly it sounds like the lighting issue is with a particular trailer. That trailer has some functions that work and others that do not. If that is correct, then it is likely there is a ground issue on that trailer wiring harness. The ground is at each tail light and most trailers also have a main ground location. These connections need to be bare metal to metal and free of corrosion and debris. If you have cleaned the grounds with some sand paper and still have issues, then you will need to use a circuit tester like # 40376 and check each wire for power/function to determine if there is a short causing the issue. If the issue is on the vehicle side, the ground is the issue because you get full function with one trailer that has a different power draw, and not all the functions on the other. This is a ground issue on the vehicle side.

Helpful Links

faq-wiring-4-way.aspx

faq-wiring-7-way.aspx

faq-wiring.aspx

tv-review-Draw~Tite-circuit-tester-40376.aspx