Left Blinker on the Trailer Isnt Working When Towed With a 2011 Ford F-150

Updated 06/07/2021 | Published 06/04/2021

Products Featured in This Question

Hook Probe Circuit Tester

(60)

$12.41

Trailer Connector Adapter w/ Lamp-Out Sensor Bypass - 7-Way RV to 7-Way RV - Vehicle End

(179)

$36.41

7-Way to 4-Way/5-Way Trailer Adapter for Vehicles with Lamp-Out Sensors Towing Trailers with LEDs

(141)

$28.54

Question:

Hello my travel trailer the left driver side blinker is not working all the other lights are working Had the service department where I bought the trailer they said everything is fine on the trailer

asked by: David

Expert Reply:

This can be caused by a few things. You will need a tester, like the # PTW2993, to check your plug, but there are a couple other things to look at as well.

First you will need to check the plug on your vehicle that the trailer plugs into. If it is a 7 Way plug, you will be testing the 9 o'clock position, which will be the left turn signal and left brake. If you have a 4 Flat plug, you will need to test the port with the yellow wire (should be the middle female port). If you are not getting pulsating power at one of these ports, there is definitely something going wrong on the vehicle side.

If this is the case, you will need to check the number 37 fuse in the fuse box in the engine compartment. This will be the one that handles the left turn signal on the trailer. If it has gone bad, you will need to replace it and retest your plug. If you are now getting power, you are good to go.

If there is still no power, odds are you have a break in the wire that handles the left turn function. This can be a bit of a pain as you will need to trace the wire to find the break. It will then need to be repaired and you will be good to go.

With all that being said, if you did get power when originally tested, it may be something else. Especially if the trailer has LED lights. Ford trucks have a computer that has had issues with LED trailer lights, so you may just need a lamp out sensor adapter, like the # 20142 for a 7 Way, or the # C35FR if you have a 7 Way on the vehicle but the trailer has a 4 Flat or 5 Flat plug.

If none of this gets the light working properly, let me know and we can try something else.