Using Atwood 1H2C Thermostat with Dometic A/C ??
I am attempting to replace a Duo-Therm Thermostat Model# 3107612.008 with an Atwood Model# 1H2C. Neither the furnace, A/C compressor, or A/C fan will operate with the Atwood. All functions are good with the Duo-Therm.
The Atwood documentation claims that it "has been designed to operate standard air conditioning units in conjunction with an RV furnace".
Furnace: Atwood Model# 8535IVDCLP
A/C: Dometic Model# 620426.331
Duo-Therm Thermostat connections:
Terminal Wire
-------- ----
+7.5 Red
Cool Yel
Fur Wht
Fan Hi Blu
Fan Tan
Gnd Grn
Atwood Thermostat connections:
Terminal Wire
-------- ----
1) Gnd Grn
2) n/c
3) +12VDC Org (voltage verified)
4) +7.5VDC Red (voltage verified)
5) Compressor Yel
6) Fan Hi Blu
7) Fan Lo Tan
8) Furnace Wht
1) The Orange wire in the thermostat cable was not used for the Duo-Therm thermostat installation, and was not connected at either end of the thermostat cable run. The Atwood thermostat requires a source of +12VDC. The Orange thermostat wire is now connected to a wire labeled "+12VDC" in the A/C wiring compartment. This "+12VDC" wire appears in a cable from the coach wiring, supplying the A/C unit. Have verified that the Orange thermostat wire is at +13.5VDC with respect to the Green ground wire. The Atwood thermostat display "powers up" upon connection of the Green and Orange wires. The Orange thermostat wire IS NOT connected to "CON 1" of the A/C controller, which apparently would be the case for a Heat-Pump / Heat-Strip application, which I do not have.
2) I note that all of the thermostat connections (with the exception of the added Orange +12VDC wire) connect directly to the A/C controller. The A/C controller provides a pair of terminals which connect to the furnace's thermostat circuit. The furnace does not connect directly to the thermostat.
3) Have experimented with the "heat" function with no thermostat connected to any wiring. The furnace goes "on" when the furnace "White" wire is connected to the ground "Green" wire.
4) Have experimented connecting to the Atwood t-stat all wires except the furnace "White" wire. The A/C compressor and A/C fan do not operate.
5) On the Atwood thermostat, there is an undocumented "dot" in the lower left corner of the display which appears to be a "Call" indicator. This appears to be functional, is "on" in "heat" mode with setpoint above room temperature, is "on" in "cool" mode with setpoint below room temperature, otherwise "off".
Does anyone have any ideas why the Atwood won't work?
The Atwood documentation claims that it "has been designed to operate standard air conditioning units in conjunction with an RV furnace".
Furnace: Atwood Model# 8535IVDCLP
A/C: Dometic Model# 620426.331
Duo-Therm Thermostat connections:
Terminal Wire
-------- ----
+7.5 Red
Cool Yel
Fur Wht
Fan Hi Blu
Fan Tan
Gnd Grn
Atwood Thermostat connections:
Terminal Wire
-------- ----
1) Gnd Grn
2) n/c
3) +12VDC Org (voltage verified)
4) +7.5VDC Red (voltage verified)
5) Compressor Yel
6) Fan Hi Blu
7) Fan Lo Tan
8) Furnace Wht
1) The Orange wire in the thermostat cable was not used for the Duo-Therm thermostat installation, and was not connected at either end of the thermostat cable run. The Atwood thermostat requires a source of +12VDC. The Orange thermostat wire is now connected to a wire labeled "+12VDC" in the A/C wiring compartment. This "+12VDC" wire appears in a cable from the coach wiring, supplying the A/C unit. Have verified that the Orange thermostat wire is at +13.5VDC with respect to the Green ground wire. The Atwood thermostat display "powers up" upon connection of the Green and Orange wires. The Orange thermostat wire IS NOT connected to "CON 1" of the A/C controller, which apparently would be the case for a Heat-Pump / Heat-Strip application, which I do not have.
2) I note that all of the thermostat connections (with the exception of the added Orange +12VDC wire) connect directly to the A/C controller. The A/C controller provides a pair of terminals which connect to the furnace's thermostat circuit. The furnace does not connect directly to the thermostat.
3) Have experimented with the "heat" function with no thermostat connected to any wiring. The furnace goes "on" when the furnace "White" wire is connected to the ground "Green" wire.
4) Have experimented connecting to the Atwood t-stat all wires except the furnace "White" wire. The A/C compressor and A/C fan do not operate.
5) On the Atwood thermostat, there is an undocumented "dot" in the lower left corner of the display which appears to be a "Call" indicator. This appears to be functional, is "on" in "heat" mode with setpoint above room temperature, is "on" in "cool" mode with setpoint below room temperature, otherwise "off".
Does anyone have any ideas why the Atwood won't work?
