I purchased a 2009 Ford F150 last fall and my running lights on my PUP don't come on when I hook it up to my truck. The brake lights and turn signals work, but not running lights. The truck lights are set to automatically come on when it gets dark enough, but even if I switch it to manually be on, I get no running lights. I hook it to my wife's SUV and the running lights work. Is there a problem with my truck wiring or is this a product of how the truck lights work?
I don't know the answer, but I'm curious. What type of connector is on your truck, your trailer and your wife's SUV? I haven't hooked my camper to my truck, but I have a 4 pin connector on my truck and a 6 pin on my camper. I bought a 7 blade connector for the truck and a 7 blade cord with junction box to rewire the trailer.
A lot of times it can be as easy as wiggling the connector when plugged into the truck. Do this in the evening so its easier to see the lights when it starts to get darker after supper. Have the lights manually turned on, and then wiggle the 2 halves of the connectors while plugged in. It might be a case of some corrosion on one of the pins making no contact. While driving the truck, the back end of the connector of the truck is facing forward and catching all road debris and rain and salt and snow and slush and everything else that gets thrown at it. That junk all gets in behind those wires and corrodes them off. You may have to pull things apart there and have a look.
Obviously not a ford, but my Silvy has fuses in the power box under the hood for trailer lights. Suggest you check there.
My truck has the 7 round or 4 flat connectors, and so does my wife's SUV. The camper uses the 7 round connector.
We bought one of these testers for our 7-pin: https://smile.amazon.com/58270-7-Wa...8&qid=1525808569&sr=1-4&keywords=7+pin+tester They also make a 4-pin tester. Checking fuses and making sure things re seated have already been suggested. We had to use a cleaning kit on the connector from our pup, but if yours works on one vehicle and not another, that's a less likely problem. (That was when we bought a dock for the camper plug, so it didn't hang out in the air and get corrosion and crud as quickly.) I do have to make sure that the plug is firmly seated in the vehicle outlet. On the 4Runner, the location made it more difficult for me to seat it well. The Colorado was OK, the Silverado is very tight, for whatever reason.
