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Old 12-13-2017, 09:43 AM   #1
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1975 25' Tradewind
milford , Michigan
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Short Circuit in Running Lights

Having a problem with the running/marker lights on my 1975 Sovereign International. We just picked up this trailer a few months ago, and almost all of the marker lights were replaced when we had the rig safety inspected so that we could get it plated.

We saw the lights in operation at the shop a couple of months ago. But when we hit the road, we noticed that we had no marker lights at dusk when our TV headlights came on ... so we pulled off the highway and stuck to daylight driving only.

We determined that the running light fuse in our TV had blown, so we replaced it. As soon as we turned the headlights on on our TV (with trailer connected) that fuse blew again.

I figured we must have a short. Confirmed this by removing all of the exterior bulbs and testing for continuity across + and - at the marker light socket. Virtually no resistance with all the bulbs removed = short circuit.

Somebody suggested that a replacement mounting screw might have nicked a wire, so I removed ALL of the mounting screws from the running lights. As a result, they are no longer grounded. But I still meter continuity across ground and running lights at the 7-way connector, with or without the umbilical attached.

Iím thinking about pulling the lights off of my Airstream to inspect whatever there is to see of wiring behind the fixture. Does this sound l8ke the right next step? Is there a better place for me to look next, perhaps the connections inside the trailer side of the 7-way?

Thoughts and suggestions apreciated !
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Old 12-13-2017, 09:58 AM   #2
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Get underneath and locate the hatch under which the umbilical from the truck connects to the wiring in the trailer. R&R the connectors.

Lynn
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Old 12-13-2017, 12:40 PM   #3
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Did you remove the tail light bulbs as well?
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Old 12-13-2017, 12:51 PM   #4
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Quote:
Originally Posted by searchcz View Post
Having a problem with the running/marker lights on my 1975 Sovereign International. We just picked up this trailer a few months ago, and almost all of the marker lights were replaced when we had the rig safety inspected so that we could get it plated.



We saw the lights in operation at the shop a couple of months ago. But when we hit the road, we noticed that we had no marker lights at dusk when our TV headlights came on ... so we pulled off the highway and stuck to daylight driving only.



We determined that the running light fuse in our TV had blown, so we replaced it. As soon as we turned the headlights on on our TV (with trailer connected) that fuse blew again.



I figured we must have a short. Confirmed this by removing all of the exterior bulbs and testing for continuity across + and - at the marker light socket. Virtually no resistance with all the bulbs removed = short circuit.



Somebody suggested that a replacement mounting screw might have nicked a wire, so I removed ALL of the mounting screws from the running lights. As a result, they are no longer grounded. But I still meter continuity across ground and running lights at the 7-way connector, with or without the umbilical attached.



Iím thinking about pulling the lights off of my Airstream to inspect whatever there is to see of wiring behind the fixture. Does this sound l8ke the right next step? Is there a better place for me to look next, perhaps the connections inside the trailer side of the 7-way?



Thoughts and suggestions apreciated !


Start where the the umbilical enters the trailer, (or the cord ends) most of the time thatís where the short will be.
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Old 12-14-2017, 10:09 AM   #5
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2005 30' Classic S/O
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I had a similar problem with our 2005 Classic when I bought it and after much head scratching and replacing of fuses found that the 12v and ground leads in the TV were opposite to those in the trailer plug, which was an easy fix. good luck
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Old 12-14-2017, 01:42 PM   #6
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1975 25' Tradewind
milford , Michigan
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Digital Multimeter helped ...

Used a digital multimeter to measure resistance at each marker light (with all exterior light bulbs removed). Found one with nearly zero resistance, which became my prime suspect.

After removing all three of the rear markers, and pulling out as much wire as I could in order to visually inspect the insulation, the short is gone!

However, I didnít spot any damaged wire ... so whatever spot of wire was compromised is still in the circuit. Iím thinking of putting it all back together and hoping for the best. Not sure if I mentioned it, but the mounting screws previously on the rear markers were ridiculously long! I replaced those 1.25 inchers with .75 inch.

Should I just put it all back together and home for the best ?
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Old 12-15-2017, 07:41 AM   #7
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Since you are this far in, I would pull out as much of the wiring from the side markers and slide some of that split wiring cover over it as far as I could and hopefully it will cover the nicked wire spot (link below). Push as much in as you can and still be able to get the lights back in properly, then cut to that length and tape it closed so it doesn't let the wire out through the slit when you push it back into the void. Get the smallest side that will still cover both wires loosely. Its cheap and you can find this at any auto parts and Walmart too.
https://www.autozone.com/starting-ch...duit/64478_0_0
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Old 12-15-2017, 09:45 AM   #8
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Start where the the umbilical enters the trailer, (or the cord ends) most of the time thatís where the short will be.
Itís good practice to replace the umbilical due to unknown age if for no other reason. Same for the breakaway switch. Iíd R&R other wiring at TT tongue just to have it done (power jack, etc).

And donít delay on full conversion of exterior lamps to LED; clearance, running and stop/brake signal. Incandescent is ďinvisibleĒ out on the highways now.
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