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Old 02-11-2008, 11:00 PM   #1
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1973 25' Tradewind
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Electrical / wiring problem

Just purchased a '73 tradewind 25'. This is my first post. Water pump switch (located in central control panel) and refrigerator will not function unless tow vehicle is attached. Anyone familiar with such a problem? I haven't had time to study the wiring diagrams yet.
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Old 02-11-2008, 11:05 PM   #2
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Do you have 12v at the pump switch? could be a bad ground that the TV's ground wire takes care of (could be the same for the hot side if you don't have 12v at the switch when disconnected). Guessing someone has a better answer but thought I'd try to help.
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Old 02-12-2008, 04:12 AM   #3
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silver bean, there is a fuse between TV feeding the 12v panel which obviously is good and also one or two fuses between the trailer's battery and the 12v panel. The 12 v panel is on the battery charger which is the third supplier of 12v when ON and connected to shore power. Does any 12v lights or appliances work when TV is not connected?
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Old 02-12-2008, 08:51 AM   #4
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Please comferm if you have anything, lights, working on 12 volts without the TV attached.

If nothing is working then I would look for a fuse or circuit breaker between the battery/converter and the main distribution fuse panel. Generaly the battery and converter have a comon output that then feeds the fuse panel through a large fuse or circuit braker. The TV power comes in on the output side of that fuse or breaker. It that large fuse or breaker was bad that would explaining why you would have power when the TV was attached.

The fact that you have power when the TV is attached proves the ground side since it is common at the fixture to all sources. As for the trailer ground circuit there is a possibility that someone may have fused the battery ground wire at the battery or the battery ground terminal is open.
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Old 02-12-2008, 09:33 AM   #5
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My 73 fuses had enough oxidation grow on the fuse spring holders no current would pass through them untill I disturbed the way they had been sitting for umpteen years - just moving the fuses in holders a little bit cleared up initial no-power problems...
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Old 02-12-2008, 11:08 AM   #6
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Thanks for the replies so far.

The lights and exhaust fans do work without the TV attached. The central control panel and radio do not work without TV attached, nor does the refrigerator.

Air conditioner and lights function when connected to shore power.
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Old 02-12-2008, 02:52 PM   #7
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Attaching the TV allows the Fans and 12 volt lights to work but if you pull the plug to the 110Volt AC tv then the 12 volt DC lights do not work. Is that right? These circuits should have nothing to do with eachother. The only thing that is common is, they are both grounded on one side. It must be something to do with the 12 volt DC ground not being connected and something inside the tv that shorts the low (neutral) side of the 110 volt ac outlets to the outlet and trailer ground. Do a ohm reading between the low side of the 12 volt appliances and trailer ground. It should be almost zero ohms. If it isn't, you will have to find out where you have a loose wire or reestablish a new connection to trailer and battery ground.
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Old 02-14-2008, 05:30 PM   #8
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Let me try to desribe this more clearly.

On Battery power - lights and exhaust fans work, refrigerator and central control (including water pump and radio) do not work

On shore power - lights and exhaust fans work, air conditioner works, refrigerator and central control (including water pump and radio) do not work

With TV attached - lights and exhaust fans work, refrigerator works, central control (water pump and radio) work

I hope that this is helpful.

Thanks again!
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Old 02-15-2008, 09:00 AM   #9
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Quote:
Originally Posted by silver bean
Let me try to desribe this more clearly.

On Battery power - lights and exhaust fans work, refrigerator and central control (including water pump and radio) do not work

This says a problem but lets look at the rest.

On shore power - lights and exhaust fans work, air conditioner works, refrigerator and central control (including water pump and radio) do not work

The air conditioner is 110 volts and should only work while the shore power is plugged in. As for the addition of the refrigerator while plugged in it could be working on 110 also. While plugged in reach in behind the refrigerator and unplug the 110 and see if that causes the refrigertor to stop working. It will take an hour or so to see the results. Other than the air conditioner and the refrigertor, which I am assuming are both working on 110 nothing has changed.

With TV attached - lights and exhaust fans work, refrigerator works, central control (water pump and radio) work

The fact that the refrigertor and control panel work while the TV is plugged in says they are getting 12 volts and OK. What it looks like is somehow the wiring from the battery to these components has been disconnected. First I would look at the low voltage fuses. They may be wired in before the splice to these 2 components. If the fuses are good I would open up the spliceing at the front of the trailer and locate the 12 volt wire to each effected item, your manual should show the color code, going into the the trailer body. Once you have found the wire feeding the control panel, and with the battery disconnected and the TV plugged in, with a volt meter detecting the 12 coming from the TV work your way back along that wire towards the battery. At some point, a splice in the wire or at the fuse, you should lose the 12 signal. If you find an open fix it disconnect the TV and connect the battery and things should be good.

I hope that this is helpful.

Thanks again!
Good Luck
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Old 02-16-2008, 10:06 AM   #10
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Hey, Silver Bean!

I've never seen a ’73 airstream, but Zeppelinium (http://www.airforums.com/forums/members/zeppelinium-10842.html) has posted some schematics for other 1970's-era Airstreams (http://www.airforums.com/forums/f37/1975-electrical-diagrams-38170.html), and they seem to provide a clue to your problem.

For starters, let's make sure I understand: when you attach the tow vehicle, the control panel, water pump, and radio work. But when you use battery or shore power (Univolt) they don't.

So we're looking for a circuit that runs to the Control Panel (etc) and that’s supposed to receive power from both the TV and the battery/Univolt…BUT only the TV power is able to energize it.

This schematic for a 1975 25' Land Yacht contains a clue (be sure you click on the image to make it large enough to read):
http://www.airforums.com/forums/attachment.php?attachmentid=50509&d=1197141624

A blue wire is connected to the 7-way connector (umbilical) at the front of the trailer, and it carries +12VDC to the Control Panel (etc) as it travels back to the "12 volt Distribution Panel", where it energizes the other DC circuits attached there. Since your Control Panel (etc) works when the TV is attached, this wire is apparently intact and functioning normally. But when the TV isn’t attached, current from the battery/Univolt can’t travel back down this wire to energize the Control Panel.

This image of the 12 volt Distribution Panel contains another clue:

http://www.airforums.com/forums/attachment.php?attachmentid=50503&d=1197141624

It shows the car battery (tow vehicle's blue wire) connected to terminal #1. That's where the TV's power is delivered to the other DC circuits. Good to know.

The photo also shows something else that surprised me, because it's an odd bit of electrical engineering unlike anything I've seen before. The blue wire is “bidirectional”…it functions in two different ways depending on the power source. When the TV is attached, the blue line delivers current to the Distribution Panel (and energizes the Control Panel on its way there). But when the TV is disconnected, it functions as "Circuit 5", which is supposed to distribute current from the battery/Univolt back along the blue wire to the Control Panel.

Okay, with these facts in mind, let's ask the BIG question: What could explain the fact that this circuit operates correctly when power is coming from the TV but not when power is coming from the battery/Univolt.

One answer could be that the blue wire isn’t properly connected to terminal #1 on the Distribution Panel. If true, then current from the TV could reach the Control Panel, but current from the Distribution Panel couldn’t. But that is NOT the problem, as proven by the fact that all of the other DC circuits operate correctly when the TV is connected. That shows us that +12VDC is able to: (1) travel down the blue wire (energizing the Control Panel, radio, etc as it goes), (2) reach the Distribution Panel without any problems, and (3) then be distributed to energize the trailer's other DC circuits. So that branch of the wiring is okay.

Another possible explanation of your problem is that current from the battery/Univolt isn't energizing Circuit 5, because it's never reaching the Distribution Panel. But that is also NOT true, as proven by the fact that the battery/Univolt can successfully energize other DC circuits like the lights and fans. So +12VDC from the battery/Univolt is reaching the Distribution Panel, but it’s not getting from there to the blue wire that is supposed to carry it to the Control Panel.

Why not?

The answer…I think (!!)...is that there is an “open circuit” within the Distribution Panel itself. In other words, once +12VDC from the battery/Univolt reaches the Distribution Panel, it’s supposed to spread out to each of the other circuits. But it’s able to reach some of them (terminals #4, 5, 6, & 7), but not others: Terminal #1 that energizes Circuit #5. So, it seems like the wire or copper trace that’s supposed to connect it to Circuit #5 is broken.

Okay…so those are my guesses based on the schematics Zeppelinium posted. Now it’s time for you to make some tests to see whether we’re on target.

You’ll need a voltmeter, whose negative lead should be connected to “Ground.” “Ground” can be “tapped” in the area of terminals #8 or #10 on the Distribution Panel). Ideally, you should connect to the left side of the shunt (??)the ammeter wires (#10) are connected to. Better yet, connect to terminal 3 (Battery negative)…but I don’t know whether that will be easily accessible. So check it out, and make a good, solid connection to “Ground” before you make the following measurements.

Here’s what I would do next:

1. Check the schematics in your manual to make sure the things I’ve said (based on the ’75 schematics) are true for your trailer, too. If you’re trailer is way different, then my ideas are probably off base. But if it looks like the wiring is pretty much the way I’ve described it, then proceed.

2. Attach the TV, and measure the voltage at Terminal #1 (the blue wire). Should be +12 VDC. Also measure it on both sides of Fuse #11. Should still be +12VDC. Also measure the voltage at Terminals #4, 5, 6, & 7. These should also be +12VDC. These tests prove something we already knew: the TV is successfully delivering current to the Distribution Panel. So far, so good. (Note: to be really, really thorough, you should disconnect the battery cable from Terminal #2 before making these tests…but I think you can safely eliminate this step for the time being.)

3. Now disconnect the TV so that battery power (or shore power via the Univolt) is powering the Distribution Panel.

4. Measure the voltage at Terminal #2 (where the battery is connected). Should be +12VDC. Also check the voltage at Terminals #4, 5, 6, & 7). These should also be +12VDC, again proving something we already knew: the battery/Univolt is successfully delivering current to the Distribution Panel.

5. Now here comes the big test. Measure the voltage at Terminal #1 (blue wire/TV). I think you’ll see that +12VDC is not present there. If so, that proves that the Distribution Panel is defective. Although power from the battery/Univolt is reaching it (and being distributed on Terminals 4, 5, 6, & 7), it isn’t reaching Terminal 1 (TV/Circuit 5).

If these tests work out as I expect, then the Distribution Panel is defective. Unfortunately, I’ve never seen a Distribution Panel like yours, so there’s not much more I can say about the nature of your problem. If the Panel is a printed-circuit board, then narrow copper “traces” etched on the back (??) function as wires and carry current from Terminal #2 (where the battery attaches) to each of the DC distribution circuits. But some older boards used actual wires soldered to the board to distribute current. Either way, it may (??) be possible for you to remove the Distribution Panel and examine it to see whether the pathway is intact that’s supposed to carry current from Terminal #2 (battery/univolt) to Terminal #1 (blue wire/tow vehicle/Control Panel). MAYBE (!!) the Distribution Panel can be repaired, but my bet is that it will be waaaay easier to just replace it.

Hope these ideas are helpful.

If you make these tests and run into anything strange, please let me know. I’ll try to help you figure them out.

Regards,

Titus
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Old 02-23-2008, 06:58 PM   #11
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Thanks for all of the advise. After many hours of examination, I finally found the source of the problem. Turns out the previous owner did some "creative wiring" and also did a good job of hiding some fuses. I located some blown fuses and once I replaced them, everything is functioning properly. I'll be improving the wiring and fuse location so I won't have this problem again. Thanks again!
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Old 02-24-2008, 07:43 AM   #12
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Glad to hear this worked out well. Good luck with the improvements you're planning.

Regards,

Titus
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