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nemo45's avatar
nemo45
Explorer
Jun 26, 2015

A/C replacement

My original front A/C quit putting out cold air. Both the fan and compressor were running. Tech said it was low refrigerant. The unit was operated thru an analog duo-therm thermostat that also operated the furnace. Since I could not replace the A/C unit with another that would operate off the analog thermostat and I would have to install a new digital thermostat and run new wires, I opted to replace it with a unit with an ADB (air distribution box) and mechanical controls and not using the original thermostat. I installed the new A/C and it works perfectly. My problem is now the furnace will not operate without the A/C in the loop. Is there a jumper I need to put on the old thermostat or reconnecting some of the wires then went to the old A/C or replace the thermostat with another that will just operate the furnace? Does anyone know how I can remedy this problem.
Class A

2 Replies

  • nemo45's avatar
    nemo45
    Explorer
    Jun 26, 2015
    Ivylog wrote:
    Does the five button Tstat still light up? If so it may be as simple as changing the dip switches on the Tstat. Here is a recent post with a phone # of a guy that may be able to help if DougRainer does not chime in. After reading the OP's quote of $4,000 to change his system over I understand why you went with a non ducted unit. I was about to do the same on my Airstream, but he had a rebuilt board for that old Duo Therm unit.
    I have three of the older Duo Therm units on my 04 Dynasty and even though they all work well, I've found a new, old stock unit as a replacement for $700 delivered that is compatible with the old CCC system. I believe in having spares and while $700 is not cheap insurance... it's better than $4,000+ to change to the new
    *OP, this trouble shooting guide may help.


    Mine is the older analog thermostat not five button. It has no dip switches. I'm thinking just buying a cheap heat only suburban thermostat is the simplest way to go.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Jun 26, 2015
    Does the five button Tstat still light up? If so it may be as simple as changing the dip switches on the Tstat. Here is a recent post with a phone # of a guy that may be able to help if DougRainer does not chime in. After reading the OP's quote of $4,000 to change his system over I understand why you went with a non ducted unit. I was about to do the same on my Airstream, but he had a rebuilt board for that old Duo Therm unit.
    I have three of the older Duo Therm units on my 04 Dynasty and even though they all work well, I've found a new, old stock unit as a replacement for $700 delivered that is compatible with the old CCC system. I believe in having spares and while $700 is not cheap insurance... it's better than $4,000+ to change to the new system.

    *OP, this trouble shooting guide may help.

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