2010 trailer LED lights don't work other than reverse lights

[Shaun315]

Which relays would those be? I see none specificly listed as pertaining to trailer functions in the owners manual. Thanks again for your help Shaun.

I doubt they're in the manual... but jumping over to the f150 forums I found this thread:




http://www.f150online.com/forums/tow...cations-4.html

I'd pull both turn/brake relays and take them to an auto store or just call your local ford dealer see if you can get the right ones. Tell the auto parts guys what your trailer does and you need to get relays with NC and NO reversed from what you have, should take care of your problem.

If they aren't located in that location you might have to find a haynes/chiltons manual, or just take it to the dealer to fix, shouldn't be that hard for a ford tech to fix (being factory wired it may be their fault anyway).

[X-Aggie]

Which relays would those be? I see none specificly listed as pertaining to trailer functions in the owners manual. Thanks again for your help Shaun.

[Shaun315]

At least pins 1 and 2 are 0V.

Did you buy this truck new? Any chance someone put the wrong relays in for the trailer lights?

It sounds like the relays are wired to the trailer with the Normally Closed (NC) relay output running to the connector instead of the Normally Open (NO). Next step is check the part numbers on the relays for the trailer indicators. If you can swap out relays with NC and NO swapped from what you have now it should fix your problem... hopefully the correct relays are the ones listed at the auto store.

[X-Aggie]

Ok truck connecter, lights and truck off:
Pin 5 = 12.25V
Pin 1 = 0V
Pin 2 = 0V
Pin 6 = 12.25V
Pin 4 = 6V
Pin 3 = 3V
Pin 7 = 4V

Lights on:
Pin 5 = 12.25V
Pin 1 = 0V
Pin 2 = 0V
Pin 6 = 12.25V
Pin 4 = 6.5V
Pin 3 = 12V
Pin 7 = 4V

Hazards on of course voltage bounced from 3-10V on all active pins

All measured +/- .3V

So I guess the big mystery is why that plug is constantly powered, and that the relay cuts power only when it should be sending power. Once again mystified.
I guess the big mystery

[Shaun315]

I guess I should have clarified, the trailer side is good. When the trailer in question is towed by other trucks it's fine. Also when I tow other boats (MC) off the lot it does the same weird thing.

Ok cool, that takes care of half the equation (and actually makes sense why your fuses aren't popping)... then you just need to check your vehicle side connector.



Try to measure from vehicle chassis ground to pins 1 (GND) and 4 (+12V) to make sure power and ground are wired correctly to the connector on the truck. Then measure the voltage from 1(GND) to the other pins with the brakes/blinkers OFF, and then with them ON to see if the brake/blinkers pins are getting +12V when the lights are supposed to be ON.

Edit--------

This thread should probably be moved into the tech section under trailers since all we're doing is troubleshooting at this point...

[X-Aggie]

I guess I should have clarified, the trailer side is good. When the trailer in question is towed by other trucks it's fine. Also when I tow other boats (MC) off the lot it does the same weird thing.

[TMCNo1]

I think they are trouble shooting X-Aggie's issue, now.

Ok, Ok, I just have trouble multi-tasking in one thread, bye!

[Shaun315]

Going to bust out the multimeter. Thanks for the suggestion!

oh yeah, forgot to ask... does the trailer behave the same way when connected to other trucks?

[X-Aggie]

Going to bust out the multimeter. Thanks for the suggestion!

[Sodar]

He said he solved it in post #23.

I think they are trouble shooting X-Aggie's issue, now.

[TMCNo1]

Can you check the voltage levels at the LEDs? Sounds like the ground is floating or is actually connected to power, and that the brake, running, and blinker LEDs share this ground. I don't think this is trailer/chassis ground though, because if it was, I don't think your reverse lights would work and you'd pop the fuse on the +12V circuit going to the trailer.

I bet when you measure the voltage at the LED when the LED is not illuminated it's ~12V on both wires going into the LED (instead of ~0V). I'd check from your truck chassis to your trailer chassis to see if there's a difference (to make sure your trailer chassis is grounded), then from the trailer chassis to the wires/contacts to the LEDs.

He said he solved it in post #23.

[Shaun315]

Work fine.

Can you check the voltage levels at the LEDs? Sounds like the ground is floating or is actually connected to power, and that the brake, running, and blinker LEDs share this ground. I don't think this is trailer/chassis ground though, because if it was, I don't think your reverse lights would work and you'd pop the fuse on the +12V circuit going to the trailer.

I bet when you measure the voltage at the LED when the LED is not illuminated it's ~12V on both wires going into the LED (instead of ~0V). I'd check from your truck chassis to your trailer chassis to see if there's a difference (to make sure your trailer chassis is grounded), then from the trailer chassis to the wires/contacts to the LEDs.

[X-Aggie]

Work fine.

[Shaun315]

I have a '97 F150 factory tow package that came with the female RV7 connect. When I use the truck to pull it does very weird things as well. Put the plug in and every light on the trailer comes on full tilt except the reverse lights. Depress brakes and they go out. Use either turn signal and when the truck lights blink (at normal pace) the corresponding LED goes out. Finally, if I leave the connector pluged in even with the truck and lights off the brake lights remain fully lit....
Works fine for everything else I pull, but I can't figure for the life of me what makes it do that for my MasterCrafts. Even more so since it's factory wired.

Do your reverse lights work at all?

[thatsmrmastercraft]

Nope. Ground was fine. It was just a loose connection when I plugged the trailer plug into the truck connector. Reck connector did not allow for a snug fit so I replaced it with a new one with a snug fit

Its amazing how simple trailer wiring is and how frustrating it can be.