Trailer running lights not working.
Thread Starter
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Elder User
Joined: Aug 2014
Posts: 560
Likes: 4
From: Anchorage, Alaska
Trailer running lights not working.
I have a 2001 F250 and my running lights on the trailer aren't working.
I have a flat 4 pin connector on my truck and I used a 4 pin connector harness with leds to test functions. Turn signals work, brakes work... Just no running lights.
I have checked all the fuses under the hood and they are good. I tried to find another fuse in my manual for trailer lights but didn't see anything.
Is there a fuse under the dash that runs the running lights for the trailer somehwere? If so, anyone have an idea on the fuse number?
****EDIT****
Just got done checking all the fuses under the dash as well. All good.
****EDIT****
Thanks!
I have a flat 4 pin connector on my truck and I used a 4 pin connector harness with leds to test functions. Turn signals work, brakes work... Just no running lights.
I have checked all the fuses under the hood and they are good. I tried to find another fuse in my manual for trailer lights but didn't see anything.
Is there a fuse under the dash that runs the running lights for the trailer somehwere? If so, anyone have an idea on the fuse number?
****EDIT****
Just got done checking all the fuses under the dash as well. All good.
****EDIT****
Thanks!
Thread Starter
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Elder User
Joined: Aug 2014
Posts: 560
Likes: 4
From: Anchorage, Alaska
Correct, I did turn on headlights. 
My buddy was saying there might be a relay somewhere behind the radio? The harness used for the trailer brake controller he said was really close to it and sometimes the relay goes bad...? I will get my multimeter out and check the brown wire on both the 4 plug connector and the 7 plug connector.
Thanks for the info.
My buddy was saying there might be a relay somewhere behind the radio? The harness used for the trailer brake controller he said was really close to it and sometimes the relay goes bad...? I will get my multimeter out and check the brown wire on both the 4 plug connector and the 7 plug connector.
Thanks for the info.
New User
Joined: Sep 2007
Posts: 16
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Here is the owners manual for your truck Look in the fuse section there seems to be a couple of fuses or relays that could be at fault.
2001 Ford F-250 Owner's Manual - JustGiveMeTheDamnManual.com
It looks like on page 175 -176 It could be fuse 4 located in the power distribution box located under the hood. I had a similar problem on a 2002 f250 I had but the fuses were located differently from 2001 to 2002 There are fuses just for the trailer wiring
2001 Ford F-250 Owner's Manual - JustGiveMeTheDamnManual.com
It looks like on page 175 -176 It could be fuse 4 located in the power distribution box located under the hood. I had a similar problem on a 2002 f250 I had but the fuses were located differently from 2001 to 2002 There are fuses just for the trailer wiring
Thread Starter
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Elder User
Joined: Aug 2014
Posts: 560
Likes: 4
From: Anchorage, Alaska
Thanks. I looked at fuses 4 and 8 multiple times, they are good. My brake controller lights up just fine. I pulled every fuse in both compartments and ohmed them out. No bad fuses.
It's got to be a relay, but the manual doesn't state where it is.
It's got to be a relay, but the manual doesn't state where it is.
Cargo Master
Joined: Nov 2005
Posts: 2,051
Likes: 10
From: TEXAS
For some reason I am wanting to say it is one of the larger square fuse that is under the hood in the power distribution box. I want to say it is fuse 100. Of course my memory isn't what it what was, but it's worth checking out.
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Elder User
Joined: Aug 2014
Posts: 560
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From: Anchorage, Alaska
Trailer Tow Backup Lamp Relay #38
Doesn't show location. I imagine its one of them relays under the hood separate from the main box. going to try swapping #38 for another relay.
Doesn't show location. I imagine its one of them relays under the hood separate from the main box. going to try swapping #38 for another relay.
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Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
The trailer tow relay is behind the left-center of the IP, in the same relay block as the turn signal flasher. To locate it, remove the radio, turn on the flashers, and follow the clicking. The relay of interest is right next to the flasher.
The output of the relay is a brown/white wire that runs to the rear of the truck. Corrosion in the several connectors from the cabin on back is pretty common.
The output of the relay is a brown/white wire that runs to the rear of the truck. Corrosion in the several connectors from the cabin on back is pretty common.
Senior User
Joined: Sep 2010
Posts: 140
Likes: 0
From: Watertown
I had the same problem and what mine turned out to be was the harness at the back of the truck. Unplug the tow harness to see if you have 12 volts at that plug. Work your way forward until you get 12 volts.
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
The trailer companies love to use crimp connectors to connect everything, even the plug pigtail to trailer. On a 12v system it does not take much corrosion to screw the connection. I just ran into light issues with my one trailer. Turned out the jack brushed the plug pigtail and pulled the wires out of a couple of the crimp on connections they used to connect the plug to the trailers wiring. I got rid of those garbage connectors and soldered/shrink tubed it now. I'll probably rewire the whole trailer when it gets warmer.
Hotshot
Joined: Oct 2006
Posts: 10,154
Likes: 7,988
From: Texas
When ever I havetrailer light problems that I cant figure out easily.......the first thing I do is always make sure The trailer lights have a good ground! A poor ground canscrew with your mind real bad