trailer lights not working
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Junior User
Joined: Mar 2011
Posts: 59
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From: gulfport
trailer lights not working
looking for info on where on the truck can i locate the relay packs or fuses for the plug for the trailer. trailer works for everyone else but mine half works(drivers side brake light doesnt work) OR MAYBE A PLUG SOMEWERE IN BEtween has came lose. need to get on highway in a couple of days need help
Postmaster
Joined: Jan 2009
Posts: 2,667
Likes: 1
From: Glen Rose,Texas
Get your book out and turn to the fuse panel section.You will find fuses that pertain to trailer lamps.Cannot remember which #.
Take a test light to the plug and check your output on signals.
Take a test light to the plug and check your output on signals.
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Junior User
Joined: Mar 2011
Posts: 59
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From: gulfport
well the fuse is ok.
i was told there fuse banks or relay banks that handle the extra load of a larger trailer lights and electric brakes all lights work ecapt the running lights on one side and the brake light on the other
i was told there fuse banks or relay banks that handle the extra load of a larger trailer lights and electric brakes all lights work ecapt the running lights on one side and the brake light on the other
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Junior User
Joined: Mar 2011
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From: gulfport
it the factory fat round pin and the small 4 pin. both have the prob
but just found out the bulb for the brake light was bad but the running light are not powered even bought the trailer pin test plug for both and thats what it shows.
it has to be somewhere between the plug and the front looked at wires seen no frays
but just found out the bulb for the brake light was bad but the running light are not powered even bought the trailer pin test plug for both and thats what it shows.
it has to be somewhere between the plug and the front looked at wires seen no frays
Lead Driver
Joined: Jul 2003
Posts: 7,404
Likes: 52
From: Wheatland, Mo
I didn't see it posted but did you check the fuses under the hood? driver's side along the fender against the firewall. THere are fuses there for trailer lights and power as well.
If this check out then I would start at the connector at the back of the truck and open it up to make sure nothing got pulled loose. Then go back from there to make sure nothing is cut. The trailer harness goes along the drivers side frame rail.
If this check out then I would start at the connector at the back of the truck and open it up to make sure nothing got pulled loose. Then go back from there to make sure nothing is cut. The trailer harness goes along the drivers side frame rail.
Veteran/Sheepdog
Joined: Feb 2012
Posts: 6,047
Likes: 110
From: Western AR
What he said...^^^^^^ Billy bob has your solution. Mine had same symptoms and I had two blown fuses under the hood in the tow control box.
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Junior User
Joined: Mar 2011
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From: gulfport
well checked under hood and the only thing i could find was two 2x3 black boxes that have relays in them no fuses. are these what ur talking about. do i need to ohm them out?????
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Lead Driver
Joined: Jul 2003
Posts: 7,404
Likes: 52
From: Wheatland, Mo
It should be about 8 inches by 5 at the top / back corner, drivers side. Your manual, if you have one, will show a diagram of fuses and relays. The top is hinged on the firewall with a little lift tab on the front that opens it up.
Now... that being said... I think in 01 or 02, they did away with that power distribution box and put it all under the dash. In the diagram tho, it will list trailer lights for tail, turn, brake, 12v power and back up. If you don't find it wait a little bit. I'll post a pick of mine.
Now... that being said... I think in 01 or 02, they did away with that power distribution box and put it all under the dash. In the diagram tho, it will list trailer lights for tail, turn, brake, 12v power and back up. If you don't find it wait a little bit. I'll post a pick of mine.
Cargo Master
Joined: Oct 2010
Posts: 2,089
Likes: 16
According to your profile, u have a 2003 model. It is pretty important to identify the year of truck you have. If that is the truck you are working on, I do not think you have the underhood power dist box. All of your fuses are under the steering column if I remember correctly. I think some of the members have had some issues with connectors under the truck corroding.
Cargo Master
Joined: Jan 2009
Posts: 2,800
Likes: 31
From: OKC, OK
Yes all 2003 fuses are under the dash. Make sure all the trailer ones are good then start with a test light at the back connector. If you don't have running lights there it might be at the back of that connector where the harness plugs in. Could be corroded.
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Junior User
Joined: Mar 2011
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From: gulfport
Sorry guys I thought all 99-03 7.3 were the same.
Mine is a 2003 extra cab not crew 4*4 fx4 auto
And this must have been when they moved it inside the cab.
Going to have another look under the dash and try to locate the bad fuses.
Will state that my truck was a boarder line total that was only two months old with 3300 miles on it the truck was put back together by a bunch of votec college kids try to pick up an extra class Bc the truck has a "diamond" in the frame they never even fixed the frame the driver wheel sits back 3/4 inch further back and they welded a pair of washers on the bumper bracket just to mount it. Praying that some idiot pulls out in front of me ( hopefully wearing there seatbelts they have insurance so one day I can fix it) its prob got all kinds of stuff wrong.
Thanks guys will report back later
Mine is a 2003 extra cab not crew 4*4 fx4 auto
And this must have been when they moved it inside the cab.
Going to have another look under the dash and try to locate the bad fuses.
Will state that my truck was a boarder line total that was only two months old with 3300 miles on it the truck was put back together by a bunch of votec college kids try to pick up an extra class Bc the truck has a "diamond" in the frame they never even fixed the frame the driver wheel sits back 3/4 inch further back and they welded a pair of washers on the bumper bracket just to mount it. Praying that some idiot pulls out in front of me ( hopefully wearing there seatbelts they have insurance so one day I can fix it) its prob got all kinds of stuff wrong.
Thanks guys will report back later
Senior User
Joined: Aug 2004
Posts: 327
Likes: 0
From: Los Angeles
I had a similar problem with my trailer lights last year. The chassis wiring harness had power but I lost connectivity in the middle of the wire between the 7 pin and the grey weather pak connector to the chassis harness. I ended up having to replace the 7/4 pin connector. It was about $140 at the dealer, but it's better than towing in the dark (or with those little test clips holding wires together).