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Help, Trailer Wiring Brain Teaser

Old 08-08-2004, 09:26 PM
  #1  
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Default Help, Trailer Wiring Brain Teaser

I have a wiring problem on the trailer and have run out of ideas for troubleshooting it. The left turnsignal does not work.
I have a converter in the truck ( 2003 Isuzu Axiom) that converts a 5 wire system to a 4 wire plug ( stop, L turn, R turn, parking, and ground) to ( L turn/stop, R turn/stop, parking and ground ). I first found that the L turn/stop (yellow wire)
was outputing voltage but no current, when I would put a load on it the voltage dropped to zero so I replaced the converter. The new one still didn't work and I then found that the 2 filaments in the bulb were shorted against each other. After replacing the bulb it still didn't work so I figured the shorted filaments had ruined the new converter and replaced it again. The new converter with new bulb still does not work.
The parking light on that side works so I know that the ground is good.
I cut the yellow wire back at the light and checked it to ground with an ohm meter and it is open (not shorted)
I tried another bulb wired direct to eliminate the plug that goes into the light socket, still dosn't work
I switched the two turn/stop wires (green and yellow) first before the converter and then after the converter and the
right signal/stop light will work from either wire but not the left.
I powered the trailer wires indepentently using a battery charger and all the lights will work from that power source
The bulbs each draw 1.6 amps when using the charger to power them.
I'm out of ideas, any suggestions would be welcome, Thanks
Dwight

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Old 08-09-2004, 03:41 PM
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Default RE: Help, Trailer Wiring Brain Teaser

Wow, Great diagnostics job!

Lets look at what you know for certain: The trailer lights work, and there is no short. The output of the converter is fine. What's left? You got it, the wire running to the converter. So it sounds like your problem is on the vehicles harness.

The only other possible thing I could think of would be a poor ground which does things that still makes me shake my head in wonder after years of messing with DC voltage. If you have a set of jumper cables lying around connect one side to the vehicle frame and one side to the trailer. I have to say I doubt this to be the problem, but as I've said I've seen stranger things happen.
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Old 08-09-2004, 03:52 PM
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Default RE: Help, Trailer Wiring Brain Teaser

re-read your post. Hmmm... sounds like you checked the vehicle side. How about a bad trailer harness connector? Perhaps the battery charger had enough umph to power all the lights but due to reistance in the connector the converter was failing to get voltage through to the left side.
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Old 08-09-2004, 04:02 PM
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Default RE: Help, Trailer Wiring Brain Teaser

dmartin,

Here is a good place to start:

http://www.geocities.com/Yosemite/23..._tips/a08.html
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Old 08-10-2004, 07:57 AM
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Default RE: Help, Trailer Wiring Brain Teaser

Are you SURE the connector is good? Cut them both off and be sure.
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Old 08-10-2004, 02:24 PM
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Default RE: Help, Trailer Wiring Brain Teaser

Don't know what you're driving, but you may have a bank of fuses under the hood you're not aware of. My last two trucks had them. Check the fuse for the left turn trailer. Took me a while to figure that one out.
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Old 08-10-2004, 09:20 PM
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Default RE: Help, Trailer Wiring Brain Teaser

Thanks for the many ideas, I finaly got time to work on the problem again and did get the lights working. I first ran separate wires to the light directly from the converter and again could not light the left turn/stop light. I could light the right turn/stop light with either the right or left output from the converter (totally confused). After lighting the right turn/stop light a few times with the converter output for the left turn/stop light, it did stop working for that light also. I was able to light either light if I connected upstream of the converter. I then bought a 3rd converter but not the "Hoppy" converter from Wally World, I got a "Valley" converter from the auto parts store. The new converter worked the first time and after reconnecting all the origional wiring I kept the left turn signal on for about 10 minutes with no problems. Bad batch of converters? I dont know, I'm just glad It's working. I also again checked the current draw for the stop lights and they are both equal at 1.6 amps, had to check it using the brakes because the turn signal doesn't stay on long enough to get a good reading. Again thanks for the ideas, you guys were very helpful.
Dwight
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Old 08-10-2004, 10:25 PM
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Default RE: Help, Trailer Wiring Brain Teaser

Funny you say that there may be a bad batch or converters. I have replaced two convertors within the last 6 mo.s. I'm on my third converter, unfortunatley its from walmart again!!
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