AC won’t turn on after removing furnace

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Stayputguy

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I threw away the furnace in 2010 keystone Springdale that is a permanent fixture on a lake lot. I did not use the furnace, it had a mouse problem, and I like the added space I got from removing the furnace. But now ac won’t turn on. I have read similar internet posts pointing to power to the thermostat as the cause of the problem. But, how do I fix it? Where the furnace had been I have 1 red, 1 yellow, 2 blue wires. Red has voltage…I touched red to yellow and blew fuse at converter box. Can I just work with these 4 wires to get thermostat and subsequently the ac working? Or do I need to tap into another 12v power source such as an outlet?
 

Gary RV_Wizard

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Look at the thermostat and see what color wires are there. Probably the blue ones. The red wire would have been the main 12v power to the furnace, not the thermostat wire.

Typically when a thermostat serves both a furnace and an a/c, the thermostat power comes from the a/c. Not the furnace. But there is no fixed rule about that.
 

Stayputguy

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187A1225-6587-4F1D-A28B-041A7C1C74CB.jpegSo most likely in this Rv the thermostat power comes from the furnace? There were no other changes other than removing the furnace. I posted the thermostat picture. At the furnace side, could I use the red wire which has 12v power to power the thermostat? Thank you, Gary!
 

Stayputguy

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Minnesota
View attachment 146957
Wires at furnace side
Did the thermostat control the air conditioner before you removed the furnace? Am I right that this is the thermostat that you have?
View attachment 146961
If it is this thermostat, then this video may be helpful.

RV Thermostat In-depth

yes. It looks like the one. And the wires match the 2nd one he showed in the video. And yes, the ac worked very well prior to the furnace removal. So, based on video, it seems the thermostat was getting 12v power from the furnace. Thoughts on restoring the power to the thermostat?
 

John From Detroit

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Davison Michigan
The problem is fairly easy to fix.. You will need a light bulb. old fashion incandascent type. and a matching socket, Dash board indicator lamp and if you can't find a matching socket a license plate socket may work both of the blade type.

ON the thermostat hook one lead to one of the FURNACE leads if they are mareked +/- or Common/+ hook to the Plus.
The other socket lead goes to 12 volt, any 12 volt
If necessary a second light assembly on the other furnace lead this one to ground.

WHY

The thermostat gets it's power from the furnace blue wires. .when you tossed the furnace you tossed the power to the T-Stat

Why the light bulbs

They act as current limiters. King of like self resetting fuses, in cae something goes wonkey
 

Gary RV_Wizard

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I've attached a wiring diagram for an Atwood 8500 series heater - yours is probably similar if not identical. The red wire is often the main power source and the blue wires go to/from the thermostat. Yes, you can use the +12v from the red wire to feed power.

Also attached is the service manual for your thermostat.
 

Attachments

  • Atwood 8500 wiring.pdf
    53.3 KB · Views: 2
  • Coleman Mach thermostat service manual-1976376.pdf
    787.2 KB · Views: 2

Stayputguy

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Minnesota
Thanks. I will connect the furnace red wire to one of the furnace blue wires when I am back at the camper this weekend. I will post the results. Thanks!
 

Stayputguy

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All is well with the AC. Where the furnace was, I connected the red wire to one of the blue wires. The first blue wire did not work. The second one I tried did.

Thanks for the help! Now on to a new problem. When I arrived to the camper, I found my dometic fridge and freezer had stopped cooling. It has power but won’t cool. I’ll start a new post if I can’t get it working! But open to suggestions here too!
 

Lawrence C. Osborne

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Jun 16, 2021
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USA
I think this may be due to the clogged coils. Please explain more about the refrigerator model.
Is it is a coil on the back without a fan model?
 

John From Detroit

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The heat exchanger (Top most outside part) can clog up on the bottom especially if you have fans on ti
The cooling unit can fail
and the control board, the heat sources (Electrical element or gas burner) and I had the connections between the controll and the "Eyebrow" fail.. pull the multi pin connector and re connectr it several times at control board (Black box on lower left) and pull the control panel (Eyebrow) straight out and do the same thing on that end.
 

Stayputguy

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Minnesota
It is a dometic 2852. I am always on shore power with battery hooked up to the camper. No breakers were tripped. Fridge is set to run on electricity only. No propane.

well, it was late last night so I emptied out the fridge and freezer with the intent of tackling the problem in the morning (all contents were spoiled so it had not been cooling for a while). I woke up this morning and the fridge and freezer were cold. Could it be that it just got too hot in the camper and the fridge went into some trip state? It had been 100F here, and the camper was all closed up while we were away for 2 weeks.
 

Lou Schneider

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On the refrigerator, the hot coils on the back of the refrigerator create a chimney draft to carry away the waste heat while drawing in cooler air from the vents in the outside cover.

When it gets hot this breaks down and you need to use a small fan to create the draft. It doesn't take much airflow but there needs to be some. Some people install one or two computer muffin fans, I just set up a small personal fan on low speed to blow air upwards past the plumbing behind the fridge when the temperature gets above 90 degrees. It keeps my fridge cold and the ice cream hard even in the 110+ heat wave I'm currently stuck in.
 

Frank B

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Calgary, Alberta
I just set up a small personal fan on low speed to blow air upwards past the plumbing behind the fridge when the temperature gets around 90 degrees or more. It keeps my fridge cold even in the 110+ heat wave I'm currently stuck in.

Great idea! Being snowbirds, we seldom camp in temperatures that high, so going to the trouble of installing fans permanently doesn't seem worth the bother. But as a quick fix under severe conditions, this is brilliant. (y)
 
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