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Old 07-23-2010, 10:05 PM   #1
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Dead short in my exterior coach tail lights

Hi Everybody,

I have a dead short in my exterior coach tail lights, including clearance lights. My 7 pin TV port is working correctly. My trailer is a 1976 31' Sovereign International center bath. When I bought the trailer last month I checked that I had brake lights and turn signals to drive the 2 miles home from the seller's place. The brake lights and the turn signal lights still work.

When I turn on the tail lights the connection blows the fuse in the TV. I disconnected the TV connection cable and opened up the panel in front of the trailer plug and I saw worn insulation in one spot on the black wire. I isolated that wire from touching anything and checked the resistance between the green wire and the white ground and the multi meter indicated a dead short. Before I used the multi meter I tried to power the green wire with a battery charger and that indicated a short as well.

I have a service manual and it shows a fuse setup for the tow plug connection in the area where the plug exits the coach, but I don't see any fuses for it. The wires are continuous and disappear under the curbside panel heading up. The interior connection cover was off when I get the trailer and there's evidence that someone may have molested the ground wire and maybe spliced it, but the green wire and others appear to be OEM and undisturbed.

Is there a fuse block for the 7 wire harness? Where?

Where do I start to look for the short?

Thanks,

Gary
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Old 07-24-2010, 03:50 PM   #2
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I eliminated my short by removing all the clearance lights and all the tail light bulbs. I didn't find the short, but I eliminated it. I'm going to replace all the clearance/running lights with LCD lights, so I may never know the source of the short.

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I tested the tail lights, brake lights, and turn signals with the battery charger, and they all work. The hitch cord trailer plug has been replaced. I found a red and grey wire on street side connected with a yellow wire nut. I don't know what those are for. That wire nut looks out of place there. I believe the black and white wires in the red sleeve on the street side are the brake wires. The brakes did work when I pulled the trailer home last month. I assume the white is the ground. It was soldered to the heavy white ground on the curb side before I took everything apart.

There are no fuses that I can find associated with the exterior lights or brakes. Do I need to add fuses?

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Anybody care to guess what the red and grey wires nutted together are?
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Click on the link to see a picture of the Sioux River falls near my home.
http://img.photobucket.com/albums/v1...g?t=1278182564
Eastern South Dakota is very pretty with hills, rivers, and trees.
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Old 07-24-2010, 04:16 PM   #3
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That's a real 'bit**' to run down...

I had a 'short' problem in the tail/marker light circuit - I worked from the front of the trailer to the rear, and of course found the problem with the bulb socket in the License plate light - the last 'link' in the chain!!!

That socket uses a two-contact bulb in the Lic Plt light, and I found the POSITIVE contact in the pigtail was rubbing on the grounded bulb socket due to a crack in the insulator that hold the two contacts for the bulb!

I cured that problem forever by epoxying an led light unit inside the chrome shield that the bulb socket was mounted in...

You should have a dedicated fuse mounted in the fuse panel for the tail/marker light circuit - my 78 does - 1.tail, 2.LH stop, 3.RH stop, 4 backup - not in that order on the panel, however...

Happy hunting!

Ray
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Old 07-24-2010, 08:50 PM   #4
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I eliminated the short. I'm replacing the bulb lights one by one.

Do you know what the two wires tied together with the yellow wire nut in my picture are? I'm wondering if they're associated with the break away switch. Is there a break away switch forum?

I can't find fuses. My service manual says they're under the cover right by the exit for the tow vehicle cord plug . . . but they're not. I suspect the PO removed the fuse block when he installed the new plug. I'll add a fuse block to be sure.
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Click on the link to see a picture of the Sioux River falls near my home.
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Eastern South Dakota is very pretty with hills, rivers, and trees.
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Old 07-25-2010, 09:57 AM   #5
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Where is your Univolt converter/charger mounted? The fuse block should be nearby....

Our 78 has the Univolt mounted forward, in the center, next to the front wall - the fuse block is mounted on the fwd wall, above the Univolt...I can't imagine anyone removing the fuse block???

Our AS uses a circuit breaker for the brake circuit, mounted next to the fuse panel...you could test those wires in question - if they're brake wires, you could apply 12 volts POS and see if the brake magnets 'sing' - or move a compass needle held next to a wheel hub...

Just some ideas....

Ray
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Old 07-25-2010, 10:56 AM   #6
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Quote:
Originally Posted by Mexray View Post
Where is your Univolt converter/charger mounted? The fuse block should be nearby....

Our 78 has the Univolt mounted forward, in the center, next to the front wall - the fuse block is mounted on the fwd wall, above the Univolt...I can't imagine anyone removing the fuse block???

Our AS uses a circuit breaker for the brake circuit, mounted next to the fuse panel...you could test those wires in question - if they're brake wires, you could apply 12 volts POS and see if the brake magnets 'sing' - or move a compass needle held next to a wheel hub...

Just some ideas....

Ray

Hi Ray,

The Univolt is under and behind the kitchen range. The Univolt fuse panel is easily accessible by a sliding door in the end panel of the kitchen base cabinet near the coach entry door. The Univolt fuse panel looks to be for the 12 volt system. My service manual shows a 5 fuse panel just dedicated to the tow cord connection. The service manual shows the tow system fuse panel under the cover at the inside front of the trailer where I show the tow plug connection in my pictures.

When I got the trailer the tow plug access cover was loose and the plug had been changed. My manual wiring diagram shows the power supply for the electric tongue jack coming from the power supply to the break away switch. the power supply for my tongue jack comes from a splice in the umbilical cord. I still have to check out the wiring to the break away switch but I'm betting it's been molested.

My wriring diagram shows there's no fuse for the brakes, the break away circuit, or the electric tongue jack except as provided by the main 12 volt power line at the Univolt panel. The only fused system to the brakes, the break away circuit, or the electric tongue jack by way of the umbilical cord supplied power, is the tow vehicle 12 volt fuse panel.

Are there any 1976 Sovereign people with intimate knowledge of the tow connection fuse issue or the break away switch connection? I'm interested in seeing an unmolested setup.

Thanks!

Gary
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Click on the link to see a picture of the Sioux River falls near my home.
http://img.photobucket.com/albums/v1...g?t=1278182564
Eastern South Dakota is very pretty with hills, rivers, and trees.
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Old 07-25-2010, 11:31 AM   #7
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7 Way plug

This a copy of the 7 way plug schematic form my manual

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Click on the link to see a picture of the Sioux River falls near my home.
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Eastern South Dakota is very pretty with hills, rivers, and trees.
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