Hello everyone, I need some help please. I am trying to find the trailer marker light wire in the dash. What color wire and were it would be located. I am hoping to find it within the headlight switch before it gets to the factory relay under the hood.

My plan is to install an always on, momentary off, switch on the dash. The idea is that I can flash my (TRAILER ONLY) marker lights/tail lights by pushing the momentary off button. I would like to do this as an easier way to say thank you to truckers who flash thier headlights to let me know it is ok to change lanes. At the moment, I have to turn off my headlights or tap my brakes to say "thanks". I don't like to tap my brakes because sometimes I'll pass while the cruise control is on and I don't like to turn off my headlights because it may freak out someone in front of me or oncoming trafic.

I have a couple of long 5ers and GN and in the next couple of months, I will be towing tandem with my smaller 5er and boat or ATV trailer. So it is nice to know when it is safe to change lanes.

The idea behind the switch is that it would always be on when the factory switch is on. When I push it, it will turn off the tail/marker lights on the trailer only, when I release the button, it will go back on. I would like to wire it before the relay so that I don't have to worry about the AMP rating on the switch. I know that I can use my own relay and put it inline on the chasis as it heads to the back, but I would prefer to keep it simple and in the dash.

Any help or ideas would be appreciated. Thanks.

 

When my "non-serviceable" (ford technical manual quote) trailer lites relay welded shut, i had to wire a relay under the dash. i removed the headlight switch, using a voltage tester found which wire was hot with lite switch turned on and used that as the control circuit for the relay. worked great. Sorry but i cant remember the wire color but you should be able to find it in couple of minutes with a tester. Hope this helps.

Good luck
B

 

Do you know if it was for the just the trailer?

 

yes it was just the trailer running lites. running lites power was supplied to the 7 and 4 pin trailer conectors all the time. got a ford troubleshooting manual and after going thru all the steps it stated to replace the circuit breaker panel. they called it an unserviceable relay.
and yes the wire i found behind the headlight switch ws just for the running lamps as well.

 

GwizRC,

From the body builders manual, you are looking for circuit 962 (BR/W) from the Power Distribution Junction Box. It is connector "J" 16-pin.

http://www.fleet.ford.com/truckbbas/...bb_pdf/170.pdf
http://www.fleet.ford.com/truckbbas/...bb_pdf/172.pdf
http://www.fleet.ford.com/truckbbas/...bb_pdf/171.pdf

Only other thing i would do, especially if you have the integrated factory TBC, is install a diode in your circuit to prevent voltage spikes or feed back in your circuit.

 

That is great info, so if I cut the wire and put the button in between, where would I put the diode? Sorry, I don't know much about diodes. What diode would I buy, I would guess that I would get it from radio shack.
Thanks, for your help.

 

GwizRC,

Put the diode between the switch and the PDJB. A diode only lets current flow in one direction.
www.kpsec.freeuk.com/components/diode.htm