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Old 08-22-2018, 04:59 PM   #1
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Identifying wires from trailer to battery

I'm trying to identify and properly connect a wire coming out of my 1984 T-2751. There are 4 wires (white, black, blue, red) exiting the trailer. White is ground to battery, black is positive to battery, blue is electric brakes.

What is the red wire and where should it be connected? It is presently not connected to anything. The breakaway device has two wires; one going to battery + and the other to blue-brakes.

Any help would be greatly appreciated.
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Old 08-22-2018, 06:20 PM   #2
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Red was generally used for +12 volts but it could be left turn. The brake device is correct.Touch the red to +12 and see what happens it not a ground.
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Old 08-22-2018, 06:24 PM   #3
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I have all exterior trailer lights working properly. Thought about connecting the mystery red wire to battery but was afraid of shorting something out, like power converter, which is presently working properly and charging my battery when connected to 120v AC.
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Old 08-23-2018, 07:16 AM   #4
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Often people twisted two wires together and it worked they then considered themselves "experts" any wiring that looks tampered with is suspect electrical tape is a dead give away. When an RV has been around for 38 years anything goes. The trailer harness end should have a battery wire going directly to the battery from the vehicle this allows the TV to charge the battery. The converter wire should also go the the battery usually fed with a #8 wire and hopefully an in line fuse this does two things it allows the converter to charge the battery and in turn powers the interior light,pump etc.from the battery. I guess my question is what does not work? If everything works it's going to be a hard call. What you can do is buy an inline fuse tap from the auto parts store connect it to the mystery wire touch the other end to the battery and see what transpires if blows the fuse that will let you know it's shorted to ground or it's some sort of ground. Early Sunlines had reverse lights maybe that's the mystery wire. I'm in the Fryeburg area where are you?
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Old 08-23-2018, 06:44 PM   #5
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Hi Mainah. I'm in Brunswick. I did a quick test and think it is a ground wire. I'm going to look and test more tomorrow to see what I can find out. I'll post results soon.
Thanks for the response and info.
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Old 08-24-2018, 08:57 AM   #6
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Red generally is not used as a ground but that does not mean a tinkerer is not color blind. I used to live in MD tidewater beyond a doubt the worst tinkered wiring I have ever seen was on boats! Other than an aircraft I can't think of anything more dangerous with poor wiring. Reading voltage to ground with a multimeter may give you false readings because it does not produce any resistance in DC stuff like that, a test light maybe more appreciate.
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Old 08-24-2018, 11:46 AM   #7
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Mainah you were right. I tried a 12v DC test light and could not get the light to illuminate using either battery terminal and the mysterious red wire.
I think the mystery red wire has something to do with the system monitor panel, specifically the battery/water warning light. Perhaps the wire is the positive feed for the warning light for the battery. The red light has always been on even though my battery is fully charged. I assumed that the light was on because the fresh water tank is empty (low water level indicator).
I connected the red wire to the positive battery terminal and the red light went out, then back on with the red wire disconnected. I crawled underneath and can see the red wire go from the trailer tongue are to directly under the monitor panel before it disappears up into the trailer.
Everything else works, including all trailer towing lights and electric brakes.

Any thoughts? I don't have a manual on the system monitor panel and this is my first RV trailer, so its all new to me.
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Old 08-24-2018, 11:52 AM   #8
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I kind of doubt the factory would run a wire that far with a fuse panel nearby however that does not mean someone trying to fix something didn't.
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Old 08-24-2018, 01:31 PM   #9
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What causes the red light on the panel to illuminate? it is labeled battery and water. Should it remain on until I fill the water tank. Guess I could will the tank with fresh water and find out. Wish I could find a link to the panel operating manual.
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Old 08-24-2018, 03:07 PM   #10
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Can't help you there mine has no panel. It is possible it indeed is a battery sense wire it goes out if the battery is at XX voltage and comes on when it drops below XX maybe someone with your type panel will chime in. Could be low water also.
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Old 08-26-2018, 07:27 AM   #11
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I don't get the light as there is a gauge for both the fresh water and battery voltage levels.
Maybe it was some kind of probe for low battery water level?
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Old 08-26-2018, 08:25 AM   #12
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Na that would be too difficult to do. I'm still thinking it is negative thinking meaning it would be on if the battery voltage is low or the fresh water level is low. It does appear to have a momentary contact switch to read the meters both for battery and water level. The holding tank lights I'm thinking are the exact opposite being on when too full. All of this still does not explain the red wire. Leaving that powered with a light on does not make sense to me the results after a while would be a dead battery long term.
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Old 08-26-2018, 09:08 AM   #13
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[QUOTE=mainah; All of this still does not explain the red wire. Leaving that powered with a light on does not make sense to me the results after a while would be a dead battery long term.[/QUOTE]

When the red wire is connected to battery positive terminal the panel red light turns off. With the wire disconnected I filled the fresh water tank and the light remained on. Reconnected the wire and light again goes out. Also turned all the lights on until the battery ran down hoping that as battery voltage dropped it would trigger the red light to come on, light never came on.
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Old 08-30-2018, 10:28 AM   #14
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I seem to remember many years ago seeing a probe inserted thru a hole drilled in the battery fill caps for a low water alert. But, I'm old and my memory plays tricks on me.
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Old 08-30-2018, 10:56 AM   #15
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Originally Posted by ggrvguy View Post
I seem to remember many years ago seeing a probe inserted thru a hole drilled in the battery fill caps for a low water alert. But, I'm old and my memory plays tricks on me.
Gary G
Hi Gary,
Thanks for the info. I connected it to the positive battery terminal so the battery red light on the panel would go out. I installed a 5 amp in-line fuse as a precaution hoping it would blow before any damage occurred. So far so good.
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Old 08-30-2018, 11:11 AM   #16
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Quote:
Originally Posted by ggrvguy View Post
I seem to remember many years ago seeing a probe inserted thru a hole drilled in the battery fill caps for a low water alert. But, I'm old and my memory plays tricks on me.
Gary G
I remember that too. Those were the old plastic inserts with a conical shape at the end of a dip-stick looking device that went into the cell where the cell filler cap was. When the battery acid/water level got too low then day light would enter in through the cap and reflect off the fluid surface simulating a light of sorts. It appeared that a light came on but it was just a light reflection using a prism. That was your warning that the water was low so you would check all cells.
When I worked in a garage years ago we raided all the old Delco batteries that had these, so that, we had one of those caps for each cell. While it was practical it was still a sales gimmick that actually worked
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Old 08-30-2018, 11:18 AM   #17
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I might add to your conversation that if you did a Google search there are wiring schematics for "international wiring codes for trailer, be they a box (utility) trailer or a simple boat trailer.
I'm sure each RV travel trailer MAY have had their own wiring protocol, but even so I believe there ARE some international coded, flat four, round seven etc.

I've always known red to be HOT or 12 VDC+ and black or white , in some cases were always ground. Other colors were marker lights, left and right (and stop) turn signal. then add the braking wire for electric brake and sometimes you'll find another HOT 12 VDC for charging the trailer as you drive.
A thicker black or white would represent ground and a thicker red would represent the hot 12vdc since those wires carry more current for the entire trailer
But, try Google for international wiring codes for trailer in general...hope that helps
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Old 08-30-2018, 11:36 AM   #18
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I believe my '79 has these wires you describe, but I haven't sorted it out yet to figure out which is which. It's definitely wired differently than newer Sunlines.
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Old 08-30-2018, 11:37 AM   #19
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Oh they still make them more for things like forklifts and golf carts most everything now are sealed batteries.
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Old 09-01-2018, 07:06 PM   #20
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Quote:
Originally Posted by JeffDonovan View Post
I'm trying to identify and properly connect a wire coming out of my 1984 T-2751. There are 4 wires (white, black, blue, red) exiting the trailer. White is ground to battery, black is positive to battery, blue is electric brakes.

What is the red wire and where should it be connected? It is presently not connected to anything. The breakaway device has two wires; one going to battery + and the other to blue-brakes.

Any help would be greatly appreciated.
Hi Jeff,

H'mm, this mystery has me really curious.

In this picture,


Those wires come out of the frame header. Have you crawled under the camper and looked where they go up into the camper? Meaning what could be directly above that location? See if inside the camper sort of directly above where it goes up, is there any kind of wood or plastic cover over the top of a small box (wire junction box). Maybe under a couch or in cabinet.

The 7 wire cord that plugs into the truck, follow that cord and let us know where it goes up into the camper. Something is not adding up that we are not understanding.

If that blue wire is a brake wire, (how did you know this?) somewhere it is connected to the 7 wire cord. By finding that connection and the other 6 wires in that 7 wire set, we can maybe backtrack into what this mystery red wire is all about. Or at least what it is not.

There is also a black flex conduit on the A frame area in that pic. What is that for and what wires are in it?

Please take pics of the 7 wire connection box when you find it. And of any and all other wires on the battery and trailer tongue.

I think your tank panel and this mystery wire are 2 different issues. That is a guess but I cannot think of what that tank panel needs a seperate run all the way to the battery to get any kind if info. But... we learn something new here on Sunline Club every day...

Hope this helps

John
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