Troubleshooting Turn Signal Circuits of 7-Way that Have 12 Volts All the Time

Updated 02/29/2024 | Published 02/28/2024

Question:

I have a 2008 Ford F-150 at the 7 pin Connector I have +12 Volts on both Left and Right Turn Signal Wires all the time even when the truck is shut off. I have removed fuse #36 and Fuse 42 so the truck brake light, upper Stop light, dont remain on constantly and run my battery down. with Fuse #36 and Fuse #42 removed the truck lights turn signal, hazard signals and brake light all work fine. Fuse #36 Trailer Tow Right turn/stop lamp Fuse #42 Trailer Tow left turn/stop lamp I dont know where the power is coming from with the two fuses removed.

asked by: Mark

Expert Reply:

Hey Mark, so what is most likely going on is that there is a short between the 12 volt accessory circuit of your 7-way and the turn signal circuits that are hot all the time. This is most likely due to a problem with the wiring behind connector due to exposed wire and if you inspect and fix that you should be good.

expert reply by: Jameson C

Mark

2/29/2024

Jameson C I have already checked the 7- pin connector and cleaned the plug on both sides with contact cleaner. The wiring is in good condition. I disconnected all the plug to the taillight and the 7-pin connector that is located just above the spare tire and still have 12 volts at fuse #36 socket non turn signals side.

Jameson C.

2/29/2024

@Mark That is a really odd issue you are having. It's hard to really narrow down the problem from here but it basically has to be something really messed up with the wiring. I know it's hard to access but there has to be something shorting out between the taillights and a power source. Maybe mice got into the wiring? A trip to the dealer or a mechanic might be only way to track it down.