Trailer Brake and Turn Signals Not Working When 7-Way Connector Plugged into 2011 Ford F-150

Updated 12/06/2021 | Published 01/12/2013

Products Featured in This Question

Plug-N-Tow (R) Vehicle Wiring Harness

(17)

$27.75

Hook Probe Circuit Tester

(66)

$12.94

Question:

Have a brand new trailer with 7 pin connector. all lights work when connected to my 2011 f150. took trailer to friends house hooked up his 2011 f-150 and all trailer lights work except the turn/hazard and brake lights. hooked back up to my truck and works. both trucks have had the relay aand fuse installed for the trailer internal power and electric brake charger.

asked by: Bob D

Expert Reply:

I would recommend checking the fuse box in your friends F-150 to make sure it has the fuses/relays installed for the trailer stop and turn lights. I looked up a fuse box diagram for a 2011 F-150 and it looked like the trailer tow left stop/turn relay is at location 37 and the trailer tow right stop/turn relay is at location 38. You will want to check the legend in the fuse box of your friend's vehicle to make sure those are the correct locations.

I would also recommend using a circuit tester, part # PTW2993, and test the functions of the 7-Way on your truck and test the functions of the 7-Way on your friend's truck to make sure that they match.

expert reply by: Jeff D

Bob

1/15/2013

found it to be fuse 73 is responsible for the turnbrake function replaced and all is good

Patrick B.

1/24/2013

Thanks for letting us know, glad it worked out for you.

Bo G.

12/6/2021

@Bob Having a similar problem on my 2011 F150. All trailer lights work on a buddy’s truck, but when hooked to my F150 all I have is running lights. Checked the voltage with a meter. Getting 2-3 volts at the plug for both the 4 and 7 point factory plugs for the turn signal and brake light pins. Getting 12.7 volts for the running lights. Also, checked the connector behind the plugs with the same results. I should mention all lights are functioning on the truck as well. All relays and fuses are good. Where should I look next? Grounding? But, I have good running lights?

Les D.

12/6/2021

@BoG Always make sure grounding it perfect. Problems with grounds make many things react poorly. On the back of the 7-way connector at the truck there should be a white wire that runs to a near by metal ground. Remove the connector and file the ground spot till clean and shiny. Do the same to the connector, the reassemble. Do the same to the ground wire for the trailer connector. Ensure that the pins in the connectors are clean and corrosion free. If this all checks out we will want to know how your trailer 4 way is wired. Does it have a factory installed connector, or was it spliced in with something like the Curt # C58044.