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Matt
Dodge Dakota
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5/02/2003
12:10:36
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 Subject: Trailer wiring blows fuse in reverse
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I have a 94 Dakota 4x4 Club Cab 3.9L V6(auto.transmission). I am using an aftermarket trailer wiring harness.
The problem is when I put the truck in Reverse, the 15A fuse blows if I have the trailer lights connected. Otherwise all trailer lights work correctly (flashers,running lights). Currently I am pulling a new ski boat trailer, but I had this same issue with a camping trailer that I pulled a couple of years ago.
Do you think that I am grounding out somewhere when I put it in reverse?
Will it hurt anything if I would try a 20A fuse to replace the 15A? Maybe it is pulling too much when the backup lights are on along with the brake lights? Just a thought.
Thanks,
Matt
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Chris
Dodge Dakota
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5/02/2003
12:13:42
|  RE: Trailer wiring blows fuse in reverse
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Do these trailers have back-up lights as well?
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Don
Dodge Dakota
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5/02/2003
15:57:39
| RE: Trailer wiring blows fuse in reverse
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I would guess that you have a short somewhere. You DO NOT blow fuses if the wireing is correct
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doug4.7
Dodge Dakota
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5/02/2003
22:57:58
| RE: Trailer wiring blows fuse in reverse
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The center pin in a 7 pin harness is called 'AUX' on many aftermarket wire sets. Which means it can go to anything or nothing. On my Dakota end of my trailer harness, that center pin goes to the backup lights (12V when backing up). If that center pin is grounded in your trailer harness, then boom! there goes your fuse. Check to see if the center pin on your trailer is grounded. If so, there is your problem.
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Darrell
Dodge Dakota
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5/04/2003
01:17:29
|  RE: Trailer wiring blows fuse in reverse
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Replace you harness, it's corroded. I had this problem last year.
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DAK2
*GenIII*
5/04/2003
09:21:22
|  RE: Trailer wiring blows fuse in reverse
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Make sure your ground wire is connected to the frame from the harness. I had the same problem until I cut the ground wire and bolted it to the frame.Cleared up the blowing fuses. The ground wire in the aftermarket harness tries to use the backup circuit as a ground to the trailer.
Y2K DAK 3.9L 5 Spd OS/2 Keeps going&going&going
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v8dakota
Dodge Dakota
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5/04/2003
22:46:30
| RE: Trailer wiring blows fuse in reverse
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I had this problem on my 2000. I returned the aftermarket harness and bought one from the Dodge dealer (about $50)
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Matt
Dodge Dakota
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5/05/2003
15:05:46
| RE: Trailer wiring blows fuse in reverse
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My aftermarket harness is a flat 4 wire type. There are not any backup lights on the trailer. The boat trailer only has a flat 4 wire connection. I am going to test out the ground wire on the truck side of the connection, and see what happens to the current when I put it into reverse. (without the motor running and parking brake on.)
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candace
Dodge Dakota
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5/05/2003
15:36:56
| RE: Trailer wiring blows fuse in reverse
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I have a '02 dakota quad cab 4.7L 4x4 with 14k on it and I have already blown a fuse from a trailer and my hook up came on the truck so it was factory installed.
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jjj
Dodge Dakota
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5/05/2003
19:33:48
|  RE: Trailer wiring blows fuse in reverse
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DAK2 hit it nail on the head. Do what he said or just cut out the ground wire on the flat plug. Don't remember which one right now. The trailer will ground itself though the ball just fine. (I know I'll get grief for this)!
Same problem as you, cut the wire 2 yrs. ago and everything is fine.
Jeff
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Matt
Dodge Dakota
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5/07/2003
09:58:01
| RE: Trailer wiring blows fuse in reverse
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I hooked up a tester last night, and got what I consider weird results. I was testing the voltage from the ground connection to the other 3 connections.(Battery only, without truck running.)
With the running lights on, the 2nd pin reads 11.4 volts, 3rd and 4th read 0.
With brake lights on, 2nd= -0.3, 3rd and 4th each read 10.5.
With backup lights on, 2nd, 3rd and 4th each read -9.7.
With backup lights and brakes on, 2nd reads -9.5, 3rd and 4th reads 1.1
With running lights/brake lights/backup lights all on, 2nd reads 1.6, 3rd and 4th read 1.1
Are these negative readings normal? Or do I have something wrong? Will directly connecting the ground still correct this?
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doug4.7
Dodge Dakota
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5/07/2003
16:12:14
| RE: Trailer wiring blows fuse in reverse
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You may not realize it, but you found the problem. Somehow, your 4 pin connector on the truck was set up wrong. The wire that SHOULD be the ground (what you call pin 1) is connected to the backup lights on your truck. That is bad. You need to fix it right away. Sniping the white wire and wrapping the end might work if you get a good ground between your trailer and truck via the hitch. You will just always have to be hooked up to the trailer to test the connections.
What is going on is when the backup lights are not on, the pin 1 is more or less ground (0V). When the running lights and left and right turn signals are on, they are at more or less 12V, so the voltage between the backup lights (0V) and the running/left/right pins (12) is 12 - 0 = 12V. You get more or less the right voltage. However, when you have the backup lights on, that pin 1 that was more or less 0V is now more or less 12V. With the any of the other lights (running/left/right signal) off, your voltage drop is 0 - 12 = -12 (more or less). So that is how you are getting negative volts. When any of the other lights are on, the voltage drop is 12 - 12 = 0 (more or less). That is why you are getting very small voltage drops when all your lights are on.
If you put the ground pin of the tester on your truck frame somewhere, you would see pin 1 of your connector go to 12V when the backup lights are on. The other 3 would be more or less 0V. When you turn on your running lights, you would see 12V (more or less) at pin 2. Pins 3 & 4 go to the left and right turn signals. When you press on the brakes, both light up. That is why when you have the brake lights on, both 3 & 4 go to 12V.
Once you have the backup lights disconnected from the 4 pin connector (on the truck end), plug in your connector to your trailer and see if the right trailer turn signal turns on with your right truck turn signal (and the same for the left side). If they are reversed, you will need to reverse the wires that go to pins 3 & 4 in your truck 4 pin connector. This should not happen, but if the adaptor was so screwed up that it puts the backup lights to the ground, I would not be surprised if the others were screwed up also. I would also find out who made the adaptor you got, find the person and give them a smack upside the head for their stupid mistake.
I hope this information was at the right level of detail.
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blk4.7
Dodge Dakota
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5/07/2003
16:36:14
| RE: Trailer wiring blows fuse in reverse
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Matt
Is the aftermarket harness the type that plugs into your existing harness or the universal type that you splice into your wiring. I've used both and the dakota specific harness is far better and easier to install.
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Matt
Dodge Dakota
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5/20/2003
10:01:39
| RE: Trailer wiring blows fuse in reverse
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doug4.7, thank you!
That explanation really got the electrical part of my brain working. So while at Walmart last night, I checked inside the package of the same type of aftermarket harness that I had. Low and behold, there was another section of 4 wires with flat-4 connections on each end, but one end only had 3 wires connected to it. The 4th wire had a connection to screw to the frame. (ie. the ground)
Being the pack-rat that I am, I dug through a box of truck stuff in my basement. I found the extra section of wire with the frame-to-ground connection.(Still had the receipt in the box 6-1-2000)
Guess that there is something to be gained from this. Maybe I should read the directions next time?!!
Thanks for everyone's comments and help.
Matt
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