Help! Running lights won't work, problem w/ truck? - Diesel Forum

565cgm · 12-12-2006, 01:48 PM

I tow my race car on an 18 foot open car hauler w/ my 2005 F250 powerstroke and have been having problems getting the running lights to work. At first, I had a grounding problem on the trailer, but fixed it and sealed everything with silicone. Now that I have tested the plug to the trailer and everything works, I have found that there is no juice coming from the truck at the plug. On the 7 pin plug, there is no voltage coming from either of the top 2 positions (running lights). I checked all the fuses and all are fine. The brake lights, turning lights, and trailer brakes work fine. Help?

Roger45 · 12-12-2006, 01:56 PM

Oh how I hate electrical problems!!! I am assuming that you have a factory installed plug.?. You need to look under the truck where the wires from the female end of your seven pin connect to the truck electrical wires. It should be a simple plug-in that is "T" shaped. Make sure that all the points are fully plugged in. If so, then you will need to check your power to this point...which means you will have to unplug it. If you have power here, then you know it is either your female plug itself (opening it up will show if there is a loose wire or two), or something with the trailer. Grounds are the most common problems, so make sure you have a good one...If you don't have power to this plug, then it is a problem with the tow rig.

Hope that gets you started in the right direction....

CaptRon · 12-12-2006, 03:58 PM

Take a look in your owners manual and find the location of the fuses for the trailer lights and under the hood for the relays. Bet that you will find that the relays haven't been installed. Most of the times they are loose in the glove compartment and need to be installed.

Capt Ron

565cgm · 12-12-2006, 04:23 PM

The lights have worked in the past. On my last tow down to Savanah from NC, they quit working about 5 minutes into my trip.

Fordman6 · 12-12-2006, 08:41 PM

The top two positions on your 7 pin receptacle are not both for running lights. The number 3 terminal (11 o'clock) should be tail lights, the number 4 terminal (1 o'clock) is your trailer batery charging circuit. So if you have power at terminal 3 of your receptacle with lights on and trailer unpluged, the tow vehicle wiring is ok, therefore the problem is in the trailer plug, wiring or lighting. If you don't have power at the recept. you have wiring or fuse problem with the tow vehicle. Hope this helps.

Bearbc · 01-04-2007, 06:34 AM

I had the same problem, I ended up ordering a new rear plug from ford, it unplugs near the spare. Problem solved. Costly though [from ford]. Good luck.

j_apetersen · 01-05-2007, 01:52 AM

sounds like blown fuse. try buying a circuit breaker. dont know were ford put the fuses but I think they are inside on a 05. they changed in 03 I think.

RattlerPSD · 01-06-2007, 11:03 AM

[ QUOTE ]
I had the same problem, I ended up ordering a new rear plug from ford, it unplugs near the spare. Problem solved. Costly though [from ford]. Good luck.

[/ QUOTE ]

If you go to your nearest RV parts store they should carry the replacement wiring for your truck / trailer connection. Try calling them before going. Compare their price wih Ford's. They are pretty standardized now and just plug right in. I had to do that on my last truck. A buddy of mine had the same problem last summer with his GM while towing. GM wanted $75 and we got it at the RV dealer for around $50.

It's a sweet set up. All the fittings are plug and go. Each is silicone sealed. I remember the days we had to install each and every wire under the screw connector. We've come a long way baby. Good luck with your fix.