Domestic DuoTherm T-stat issues

1. Check the Front AC Board(which is Zone 1). There are DIP switches on the board. turn them all OFF and then turn the ones you need on. Furnace should be the only one ON unless you have a Heat Pump then turn it ON. Go to the Rear AC(Zone 2). Turn off all the DIP switches and only turn on the DIP switches you need. probably just Zone 2. IF you have a Heat Pump, turn it on. I doubt you have 2 furnaces. If you do, turn on the DIP switch for furnace. That makes sure the DIP switches are set. Do a Tstat reset to verify the DIOP switch configuration. SYSTEM RESET
After setting the dip switches in the electronic control
kit, do a system reset.
1. Turn the ON/OFF switch to the "OFF" position.
2. Simultaneously depress and hold the MODE and
ZONE push-buttons while turning the ON/OFF switch
to "ON". FF should appear in LCD display until the
mode and zone push-buttons are released.
Now, if you still have a problem, disconnect the Phone type cable at the front AC. There are 2 if you have 2 roof AC units. One goes to the tstat. The other goes to the rear AC. If you disconnect and loose power to the wall tstat reconnect and disconnect the other cable and see if Zone 1 operates correctly. IF it does, the problem is in the com cable from AC 1 and AC 2. Now, do you have Penguin Roof Units? IF so, the odds are after 17 years, the COM phone cable connections in the evap area of both units are corroded from humidity. looking at the phone type modular connections and disconnecting and if you see rust and corrosion that is your problem. Doug

After doing a reset, it constantly says EE. I only have 1 rooftop ac. Currently the dip switches in closed position are 3, 5 and 6. 1 is heat strip 2 is zone 2 3 is zone 3 4 is zone 4. 5 is furnace 6 is differential 7 is stage and 8 is generator start.

MagicMikeD wrote:
After doing a reset, it constantly says EE. I only have 1 rooftop ac. Currently the dip switches in closed position are 3, 5 and 6. 1 is heat strip 2 is zone 2 3 is zone 3 4 is zone 4. 5 is furnace 6 is differential 7 is stage and 8 is generator start.

That means COM error. You have a problem with that phone type COM cable. DIP are ON or OFF. OFF is what the majority should be. Furnace should be ON. All others OFF unless you have a Heat Strip. Doug

Thank you sir! I created a custom cable and it worked!! I'm hoping I can just cut the ends off and re-terminate and the corrosion hasn't went back through the cable. Thank you for all of your help!