Coleman two wire thermostat wiring

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  #1  
Old 08-10-15, 08:36 PM
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Coleman two wire thermostat wiring

I am working on a 2 wire setup on a Coleman furnace, in a mobile home. It has a switch on the furnace for Heat/Cool and Fan - Auto/Run. Currently it is wired to control the heat only. Switching the furnace to cool, turns the cool on but the thermostat does not shut it off, even when it is making ice cubes . Anyway, I found an old string talking about the same issue and they got it working, but I don't understand it. I'm ok switching between heat and cool, but just want the thermostat to turn off both heat and cool.

Here is a link to that string: http://www.doityourself.com/forum/ai...rmostat.html#b

Or here is the important text where the question is asked and the answer given.

Question: Wiring a 2 Wire Thermostat

I am trying to wire my New Honeywell programmable thermostat. The existing Thermostat uses only 2 wires (for heating and cooling). The switches for Fan operation and Heat/Cool are on the unit itself. I have wired it correctly for heat all winter, but the cooling has me stumped.

When switched to heat, if the 2 wires are connected (jumped) the heat will go on - when disconnected the heater will go off. (this works fine with my thermostat).

When switched to Cool, it is opposite. If the 2 wires are connected the A/C is off, but turns on when the wires are disconnected.

I dont care if I have to rewire this thermostat every season, but I would like to get the thermostat to work with cooling right now. This must be possible in some way, but I have not seen anything on the net about a 2 wire system that heats and cools.


Answer
On a two wire Coleman, you ignore the heat/cool switch on the new stat and always leave it in heat. There should be a switch at the furnace for heat and a/c that is actually a reversing relay. Using the switch at the furnace should solve your problem.

Followup
Glad it worked for you...by switching at the furnace, it's reversing the polarity of how the stat activates. Closed contact in heat produces heat. An open contact in cooling, activates cooling and that's why it will run in the off position, the contacts are open. (Relying on switching at the furnace when you need heat or cool) It's basically a manual fan control center that Coleman/Evcon put in their older systems. The new ones are 4 wire now.
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  #2  
Old 08-10-15, 08:46 PM
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So..... what would your question be ?
It looks like the wiring was covered in that other thread.
 
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Old 08-11-15, 01:29 PM
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What I was saying is that I don't understand how they are saying to wire it, so my question is where does the red wire go and where does the white wire go. And if I need a jumper wire, where does it connect? Finally, how are the onboard jumbers to be set? HE or HG and B or O?
 
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Old 08-11-15, 01:50 PM
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HE is for electric heat and HG is for gas heat. B/O is only used on heat pumps. The stat should be wired like the first pic.
 
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Old 08-11-15, 01:59 PM
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But when wired as in the first pic it doesn't shut off when on cool.
 
  #6  
Old 08-12-15, 06:26 PM
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Are you replacing an old thermostat, did it work before you started this conversion?
 
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Old 08-12-15, 07:17 PM
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Oh....ok. You have a Coleman furnace that was modified to run A/C.

When switched to Cool, it is opposite. If the 2 wires are connected the A/C is off, but turns on when the wires are disconnected.
I missed what you said earlier.

You connect the red wire to R and the white wire to W/aux.
The thermostat will ALWAYS be left in the heat mode. You cannot use the cool or off postion.
Cool or Heat is changed only at the furnace.
 
 

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