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Old 07-10-2006, 07:31 PM   #1
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1977 31' Sovereign
Erie , Pennsylvania
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12v Negative Problem

Hello All.
I got the new (to me) '77 31' Sovereign home last week. Spent all weekend cleaning and repairing what I could when all of the sudden all the 12v power stopped. So I got out the handy tester and discovered the univolt was putting out no power, it was plugged in and humming. I read on here that it's probably bad so I ordered an intelli-power. Anyway, it was getting dark out and I really needed the lights so that I could see what I was doing, so I hooked up the battery (fully charged) and got nothing. I poked around with the tester a little more and discovered that there wasn't any connection being made between the four spots where the negatives connect and the negative on the battery. The fuses weren't blown. The only way that I could get the power to work is by connecting the negative from the trailer to the battery directly. I hooked the univolt back up the same way to see if it would work and didn't get anything. I've attached a picture of the area. Any ideas on what's wrong here before I get the new unit hooked up?
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Old 07-10-2006, 08:45 PM   #2
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you will find a fuse on the negative lead.

they are in various places on different trailers. look for it just below the univolt. it should be on a fiber block all by itself. it is a large glass fuse.

follow the large black lead and you will find it!

john
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Old 07-10-2006, 09:51 PM   #3
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Wink No Fuses

Thanks for the reply, there aren't any other fuses on any of the main wires except for the ones on the fuse panel. They aren't there in the picture, but they were plugged in and are good when I had the problem, the negative ones are on the top left. The univolt was wired diretly to the panel. The negative from the univolt connected to the bottom left of the 4 terminal area, and the positive was connected to the bottom of the battery fuse (not in the picture). There are also no other fuses between the fuse panel and the battery.
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Old 07-10-2006, 11:17 PM   #4
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It looks as if the item in the top center may be a circuitbreaker.
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Old 07-11-2006, 07:07 AM   #5
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The item in the top center is where the 12v connection from the hitch connects to the electric jack and then back to the distribution panel. There doesn't seem to be anything wrong with that. I think my issue is with that large flat square thing where the ammeter hooks up that is in the bottom center of the picture, I'm just not sure what the problem would be. Everything seems to be touching but nothing gets through.
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Old 07-11-2006, 10:01 AM   #6
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I had the same problem....I just installed a WFCO converter from bestconverter.com and everything is well. I did have a 50A fuse on the negative battery wire that was mounted between the univolt and the battery.
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Old 07-11-2006, 11:08 AM   #7
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Sounds like time for some ohmmeter checks on all the lines and connections. Also check from negative to trailer frame.
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Old 07-11-2006, 11:59 AM   #8
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do you have a wiring schematic of your coach? That would help, they are in the users manual.
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Old 07-11-2006, 03:14 PM   #9
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Quote:
Originally Posted by dwightdi
Sounds like time for some ohmmeter checks on all the lines and connections. Also check from negative to trailer frame.
What would this accomplish?

I do have the wiring diagram from the owners manual, but it is not helpful at all, it just says what colored circuit the fuses goes to, which doesn't tell me much.
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Old 07-12-2006, 03:53 AM   #10
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meter

definetly need to meter everything out. sounds like the negative is open somewere between battery and univolt or univolt to fuses. if i'm not mistaken there looks like you have a couple fuses missing in the pic. i would even check the univolt itself to see if your getting 12v out. i would start w/ neg. to frame as mentioned.

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Old 07-12-2006, 06:37 AM   #11
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Quote:
Originally Posted by jrk247
What would this accomplish?

I do have the wiring diagram from the owners manual, but it is not helpful at all, it just says what colored circuit the fuses goes to, which doesn't tell me much.
It would enable you to determine where the circuit is open. I assume you cleaned everything up.
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Old 07-12-2006, 10:19 AM   #12
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Quote: got the new (to me) '77 31' Sovereign home last week. Spent all weekend cleaning and repairing what I could when all of the sudden all the 12v power stopped. sounds like the univolt crapped out. So I got out the handy tester and discovered the univolt was putting out no power, it was plugged in and humming. I read on here that it's probably bad so I ordered an intelli-power. good so far. Anyway, it was getting dark out and I really needed the lights so that I could see what I was doing, so I hooked up the battery (fully charged) and got nothing. I poked around with the tester a little more and discovered that there wasn't any connection being made between the four spots where the negatives connect and the negative on the battery. The fuses weren't blown. The only way that I could get the power to work is by connecting the negative from the trailer to the battery directly. I hooked the univolt back up the same way to see if it would work and didn't get anything. confirms that the univolt is bad. I've attached a picture of the area. Any ideas on what's wrong here before I get the new unit hooked up?

from your description and the picture, i would guess that the PO had disconnected the battery from the univolt by removing the fuses from that fuse block in the lefthand side of the picture. your coach was then running on univolt power, and when it failed, the battery was not in the picture. if that's the case, a voltmeter reading across the terminals of the fuse block would probably be about 12 volts, if you have one light turned on to complete the circuit. (guessing that the battery side of the fuse block is connected to the negative terminal of the battery.) well, that's my guess as to what happened.
good luck.
and
regards
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Old 07-12-2006, 05:51 PM   #13
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Ok, when I take the ohm meter to the circuits I get no reading...meaning there are no shorts right? When I take the ohm meter from the 12v negative to the frame I get a reading...which I should correct? I've attached a marked up picture of the way the wiring was done before I disconnected them and attached the 12v negative from the circuits directly to the negative for the battery. As I previously mentioned the fuse was installed and is good. When I connect the ohm meter to the four incoming negatives to the fuse to the battery I get nothing. When I take a reading across that flat plate I don't get anything either. So would removing that plate and replacing it fix the problem...i'm no me/ee, but I don't think that metal can just stop conducting electricity right? I guess that that area just needs rebuilt to work?

Thanks
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Old 07-12-2006, 06:03 PM   #14
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I see a possible problem...

Maybe. Is that a 12v charge line from the tow vehicle hooked to the three ground wires (univolt, chassis, and battery)? The charge line is positive as well, if that is what I am seeing.
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