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Discussion Starter #1
When I hook up my boat trailer to my truck I have been blowing fuses automatically. What goes is the fuse that runs my running taillights for both the truck and the trailer. Brake and both signals still work, but if I wanted to run in the dark, I can not go.

I am wondering if you think it would simply be an issue of a short in the trailer (where it may be pinched or rubbed) or if you think it is an issue with the truck harness itself. A little history on my truck. I bought it in the U.S. last year, and in Canada I had to have daytime running lights hooked up to meet the safety inspection. Well, I got a dealership to hook up a trailer harness at the same time as they did the daytime running lights.
I also just bought the boat and trailer used so it is not like it just started on me, I don't know any different at this point. I would like to get this sorted out though.
 

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Griff
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914 Posts
it doesn't have anything to do with the daytime running lights.

i would first search for a place on the trailer where a wire may be rubbing/grounding itself out. if you can't find a solution, hook your truck to a different trailer and see if the fuse blows then. if not, it's the trailer that is causing the blown fuse. if it still blows with the 2nd trailer then bring the truck back to the dealer and have them figure out what may be blowing the fuse.
 

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Native Oregonian
07 Tacoma DC LB TRD
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785 Posts
I think its pretty straight forward here. If your truck doesn't blow a fuse until the trailer is hooked up, then you have a problem in the trailer. You're only going to blow a fuse for one reason, overcurrent. Since it hasn't blown without the trailer, obviously the trailer is drawing too much current, indicating a short to ground. It shouldn't be too hard to find I'd hope. Take a multimeter and measure all the pins on your clip to ground. I do believe only one of the 4 (assumign you have a 4 pin) will actually be ground. The other three will read a moderate resistance through the light bulbs, but definitely not a short.

Boat trailers are notorious for wiring problems... I mean think about it, you dump them in the water all the time.
 

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Stupid is stupid does
2008 tundra
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5,554 Posts
I think its pretty straight forward here. If your truck doesn't blow a fuse until the trailer is hooked up, then you have a problem in the trailer. You're only going to blow a fuse for one reason, overcurrent. Since it hasn't blown without the trailer, obviously the trailer is drawing too much current, indicating a short to ground. It shouldn't be too hard to find I'd hope. Take a multimeter and measure all the pins on your clip to ground. I do believe only one of the 4 (assumign you have a 4 pin) will actually be ground. The other three will read a moderate resistance through the light bulbs, but definitely not a short.

Boat trailers are notorious for wiring problems... I mean think about it, you dump them in the water all the time.
X1
 

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J.O.A.T, Master of none
'14 Tacoma DC/LB
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2,691 Posts
You could buy yourself one of those $5 trailer plug testers, just a trailer plug with LEDs on it. If all sequences work, it's your trailer wiring...which it will undoubtably be anyway. Some people don't realize that there is a standard for trailer wiring, some don't adhere to it putting the ground on the wrong wire.

I check my trailer wiring with a battery charger, ground the negative pin and touch the plus side to each individual pin on the connector. You'll know the ground pin on the plug, it's the only one that is different. If you find one circuit that draws a lot of current, you can begin to trace from there. I'll bet that you have some yahoo wiring from the last owner. The odd connector pin is ground and should be white.... brown, green, and yellow are light circuits.
 

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Premium Member
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2,629 Posts
If you don't have a multimeter, get a cheap one like this
http://www.radioshack.com/product/index.jsp?productId=2999093
or
http://www.sears.com/shc/s/p_10153_...hop&sName=Multi-Meters,+Testers+&+Accessories

Check the truck first, non-factory installs have been known to be wrong. Using the diagram phantom pointed you to, set the meter to 20VDC or greater, hook the black to ground, then touch red to the various wires. 1st turn parking lights on, look for voltage on only that pin, the rest should be off
2nd, turn your flashers on, look for intermittent voltage on two pins (left and right turns), the rest should be off. If anything above fails, your truck may be mis wired. Step 3 is left turn, step 4 is right turn, if step two fails

Next, switch meter to 20Ohms resistance, and move to the trailer. Hook one probe to a grounded point on trailer, then touch each wire in turn. Should see 1-5ohms on your ground, then open on the rest. If any show low ohms, that's where your short is.

If you set the meter to 200 or 2K ohms, you should get a reading on other points besides ground, due to resistance of the light bulbs.

The fittings that get submersed are often bad, rust and crud shorting the sockets out. pull the bulbs, look for bad things. I've seen trailers with the short about 2' down the tube from the hitch, as the wire swings back and forth while turning, and just plain wears the insulation out. Easier places to look are anywhere that the wires enter or exit a tube, the wire will wear on the edges.

Have fun.
 
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