Originally Posted by
Lorijohn
97 F150
I seem to have a similar problem, but it is the same even if trailer is not attached. I've checked the 4 pin plug with volt meter and also checked the pins on the wiring harness plug in the fender well. The both operate the same strange way. Checking the voltage at each pin with the ground on the 4 pin plug I get the following voltages:
..........Brown yellow green
all off.....12.......0.......12
brake.....12.......0.........0
lights.......0.......0........12
LB..........12....0/.15.....12
RB..........12......0.......12/0
light&brake..0....0.........0
Is this a ground problem too or a wiring failure somewhere else. The truck lights themselves work fine. I checked all the trailer fuses, including the one in the small 5 slot box near the firewall. They all look good. I apprecite any suggestions.
John
The brown wire is the running lights. The yellow and the green are the turn/stop lights. The white is the ground.
I don't have a schematic of a 97 f150. But go to the fuse box up under the dash and also under the hood, and see if you can find some relays. See if you can find a trailer marker lights relay. You may or may not also find some trailer turn relays in another box under the hood. If you find any of these relays, pull them out and then do your voltage checks again.