Trailer light issues
Fleet Mechanic
Joined: Aug 2006
Posts: 1,465
Likes: 17
From: Jacksonville, FL
is it on one specific trailer or any trailer? because it sounds like it is a couple of different trailers if you have used both the 7 and the 4 pin?
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Senior User
Joined: Aug 2003
Posts: 393
Likes: 2
Its on my 3rd brake light under tailgate but also did it to the trailer. I thought maybe it was the 3rd brake light but it was both. I tried it with my 7pin to 4pin plug in and the 4 pin. I thought maybe it was my trucks 4pin but it was both. Im thinking its something to do with my trailer hook ups on my truck. something grounding out etc.
Fleet Mechanic
Joined: Aug 2006
Posts: 1,465
Likes: 17
From: Jacksonville, FL
Its on my 3rd brake light under tailgate but also did it to the trailer. I thought maybe it was the 3rd brake light but it was both. I tried it with my 7pin to 4pin plug in and the 4 pin. I thought maybe it was my trucks 4pin but it was both. Im thinking its something to do with my trailer hook ups on my truck. something grounding out etc.
Hotshot
Joined: Feb 2003
Posts: 11,537
Likes: 27
From: Long Beach, Ms.
If it blows when you plug the trailer in, it's the trailer. Otherwise it would blow on it's own if it was the truck. I recommend having one of these in your towing kit; 12" Extension w/ 4 Wire Trailer Wiring Pigtail Tester :eBay Motors (item 200345031116 end time Jun-21-09 10:13:37 PDT)
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Senior User
Joined: Aug 2003
Posts: 393
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If it blows when you plug the trailer in, it's the trailer. Otherwise it would blow on it's own if it was the truck. I recommend having one of these in your towing kit; 12" Extension w/ 4 Wire Trailer Wiring Pigtail Tester :eBay Motors (item 200345031116 end time Jun-21-09 10:13:37 PDT)
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Elder User
Joined: Jul 2008
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From: Newport, Wa.
Any time the back-up light fuse blows is because it has a path to ground without any load, ie. lamp bulbs.
My question is what else does this fuse supply for a trailer? The seven pin connector has the same four supplies as above with the addition of battery charging, trailer breaks and perhaps back-up lamps. ah-ha.
So, when exactly does your fuse blow? When you first plug in the trailer? or when you turn on the lights? or when you apply the breaks? or when you put the truck into reverse?
Let's pin this down first. BTW, your not the first one to have this problem.
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