Trailer Lights Blinking Really Fast When Connected to 7-Way on 1997 GMC Yukon

Updated 05/23/2024 | Published 05/11/2015

Question:

Hi Jim here, I just purchased a 1997 GMC Yukon with factory 7 wire tow wiring and my trailer has 4 wire so I hooked up an adapter and when I turned on my truck lights the tail lights worked, brake lights worked when I turn on my left turn signal my 4 ways come on. when I my right turn signal nothing works. I purchased what looks to me to be this part 118319, or very similar I disconnected the splitter and plugged in the new splitter I purchased at tractor supply and ran the 4 wire directly to my trailer and everything works but my turnsignals are rapid firing, blinking really fast. I unplugged the 4 wire from my trailer and plugged it into my 7wire port and plugged in my trailer using the 7 to 4 adapter and I got the same result out of control turnsignals. Any ideas/ Thanks

asked by: Jim

Expert Reply:

When someone is experiencing out of control or hyper flashing turn signals, a few things come to mind.

First would be, does the trailer have LED lights? If so, installing load resistors, # DI34ZR, on the turn signal circuits should solve the problem. LED lights only draw a fraction of the power that an incandescent light would so vehicles with a bulb-out sensor are tricked by this and think that a bulb has burned out which in turn causes the rapid blinking. I have included a diagram showing the proper installation of the load resistors.

If your trailer does not have LED lights I would start off by checking the wiring on the trailer. Check to make sure that the ground wire is secured to a clean metal surface on the trailer. In addition, each lamp/signal will also need to be grounded. Typically the lamp/signal is grounded through the mounting bolts having direct contact with the trailer frame. Also check the trailer connector to make sure that it is free of dirt, debris, and corrosion.

Next I would move on to checking the bulbs on the trailer. It is possible that a bulb could be going out which is throwing the system off.

If you still find that your turn signals are not functioning properly, please feel free to send me an email and we can continue with troubleshooting.

expert reply by: Leah S

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Rick S.

5/9/2024

there are 2 wires on the resistor. does it matter which of the wires on the resistor is connected to the + and which is connected to the ground? thanks