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Old 08-01-2012, 10:11 AM   #1
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Hotwiring 12 volt to duotherm 11.5 btu a/c

A tire blowout took out 12 volt harness to a/c unit. Will be in Dallas for 2 days in over 100 degree temp, so am desperate to get unit working. Thermostat power has no voltage. Can I run 12 volt wire directly from fuse terminal to a/c unit overhead? Two blue wires inside a/c labeled electrical. Need clear instructions. Will have 110 at camp site. Thanks.
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Old 08-01-2012, 10:25 AM   #2
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If you have a wall-mounted thermostat, it seems like it might be easier to directly run 12v to the thermostat and still have control over the AC (though with current DFW weather, "On Full Blast" is the only setting you're likely to need!)

If your controls are on the AC unit but require 12v, I've got nothing...
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Old 08-01-2012, 11:46 AM   #3
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The A/C unit provides the power to the Thermostat. Don't run 12 volts DC to it. This could damage the internal components of the A/C unit.
If you must run the A/C then locate where the thermostat wires are in the unit. There are two wires that are nothing more than a switch leg. 12 volt power either AC or DC is fed from the A/C unit to the thermostat then the second wire carries that 12 volt power back to the A/C unit when closed.
You can locate the two wires and their termination points. Disconnect them and install a jumper or a temporary thermostat could be wired in at this point.
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Old 08-01-2012, 12:36 PM   #4
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Quote:
Originally Posted by RichHog View Post
A tire blowout took out 12 volt harness to a/c unit. Will be in Dallas for 2 days in over 100 degree temp, so am desperate to get unit working. Thermostat power has no voltage. Can I run 12 volt wire directly from fuse terminal to a/c unit overhead? Two blue wires inside a/c labeled electrical. Need clear instructions. Will have 110 at camp site. Thanks.
12VDC needs to fed directly into the upper A/C unit control box and NOT INTO THE THERMOSTAT on a Dometic CCC controlled unit. There will be 2 12VDC input wires located along with 2 yellow wires (not used), the thermostat control wires for the furnace (blue wires) and possibly a couple of others. IT IS HERE THAT 12VDC should be inputted into the control board. The wires for 12VDC should be red and black, or have appropriate labels on them.

All communication, from 12VDC input to the comm data to and from the CCC occurs along the data cable that resembles a phone cord. The only connection that should be made is by 4 pin RJ-11 type plugs into the rear of the CCC and then to the appropriate plug-in at the upper unit.

No other connections will allow the unit to work and will probably damage your electronic components in the unit.
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Old 08-01-2012, 01:52 PM   #5
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Lewster is right. You'll want to run 12v up to the air conditioning unit. Drop the air distribution box by removing the screws and look for the wires. In general there will be the flat grey phone-type wire to the thermostat, a pair of wires to the furnace, and another pair of wires that supply 12v power, all going into the trailer frame in more or less the same spot. I would suggest cutting the wires so you don't have to worry about the possibility of a short where the wires are damaged. If you guess wrong and hook up to the furnace pair it won't damage anything but won't work.
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Old 08-01-2012, 02:06 PM   #6
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Ac

There are 2 blue wires labeled electric from the factory and wirenutted to feed cables. I tried hooking the thermostat into a direct connection to the overhead unit but nothing changed. Problem is getting 12 volts directly to the unit. Car says its 107 degrees in Dallas
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Old 08-01-2012, 02:19 PM   #7
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Rich you do have the newer Duotherm setup with the electronic thermostat, don't you?
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Old 08-01-2012, 04:21 PM   #8
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AC out

It is the newer thermostat that has a 4 pin phone style connector that runs to the AC unit
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Old 08-01-2012, 04:29 PM   #9
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AC connections.
Red and blue connected together
Black and white connected

Blue to blue thinner wire connected
Labeled electrical
Blue white to blue thinner wire also labeled Electrical
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Old 08-01-2012, 11:13 PM   #10
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Works

Thanks Lewster for getting it right. Cut the red and blue wires and ran a red extension from the fuse box and wirenutted it together and bingo the thermostat lit up, AC came on. The blue wire goes back to the broken connecter. Worked for about 15 minutes and then through the AC breaker. Just reset it and it's back on. Fingers crossed.
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