I just purchased a trailer and come to find out that my left turn signal is not working on the trailer. It works on the truck but not the trailer. When I turn on the left turn signal and go to the fuse box in the engine compartment, I can hear the relay clicking. I can not hear any clicking when I turn on the left turn signal. I switched the left and right relay and can still only hear the right relay. That says the left relay is good. Is there a fuse or something that I need to replace? I can't find it in my user manual. Any help will be appreciated very much. Thanks in advance.

 

I think that your trailer relay is bad or you may have a bad connection to the trailer. try having some one step on the brake and check to see if both lights work on the trailer if not then your left bulb is bad if it does work then your relay is bad and that's not under the hood that's in the back under the truck. you didn't tell what the model of your truck is and if your turn and brake lights use the same bulb or not

 

I was inaccurate with my problem description.

First, I have a 2009 Ford F150 King Ranch 2WD Crew Cab.

Second, my problem is that all functions WORK on my truck, but NOT on my trailer. Specifically, the left turn signal does not work and the left stop light does not work. I have focused on the left turn signal and REPLACED the relay under the hood. Still does not work. When I open the fuse panel under the hood, I can hear the relay clicking for the RIGHT turn but not for the LEFT turn. In addition, when I remove the relays that are under the hood and use a test light, I see where I get a blink signal to the right relay but NONE to the left relay. I am starting to believe there is a wire problem from the "under the dash" relay to the left relay under the hood".

Any recommendations to troubleshoot the problem will be greatly appreciated.

 

does it work without the trailer hooked up?

 

The way the system works is,,

The Smart Junction Box has a micro processor that controls the pulsed voltage for the truck/trailer. Being it works for the left lamp flash on the 'truck', should take the SJB out of the diagnostic (as well as the SJB #6 fuse for circuit protection for 'both' R&L processor lamp functions) for the trailer lamp relays.

Power distribution for the trailer lamps (load) for 'both sides' R&L is in the Battery Junction Box fuse #45. Being the right side works would take a fuse issue out of the search as well since the fuse protects both traler lamp relay/loads.

If your probing the L relay connector and don't have any pulsed voltage, (R was ok) I might first check the harness area at the back of the BJB (Gray/Brown tracer) and see if the circuit is active there. There is a loom splice in line, but doubt it would be an issue.

You could also check/confirm the connector at the SJB (pin 25-GY/BN wire) for a pulsed voltage (interrmittent?), but it would be there since the truck functions normally. SJB is in the right kick panel.. With a pulse there, and nothing just before the BJB (?), there's an issue in line.. As a test,, you could probe the SJB GY/BN and run a test lead out to the BJB Left relay. Wrap a single 'thin' copper wire strand around the pulse leg of the relay (as positioned on the right relay) and plug the relay back in.. Left should function if the ground, and load out to the trailer connector are good..

 

Thank you Hayapower. I am going to work on this later today when it cools off outside. I have been concentrating on the trailer left hand turn signal, but in addition to that, the left hand brake light and the Left hand Hazard light do not work. I hope they are all interrelated!!! Essentially, the left hand running lights work and that is it. Also, if you have the wiring diagrams or know where I can get them, it would be greatly appreciated. I ordered them today but it will be a week before they come through the mail.

 

I solved the problem. After getting into the BJB wiring, I saw where someone had to add jumpers to 4 wires. Guess there must have been a problem. Two of the 4 wires were wired back correctly. There were two gray with brown stripes that were cross wired. After I put them back in the correct position, everything worked. Thank you Hayapower for your help. I would have never known what to look for.

 

Glad you got it fixed, and for the update..