furnace/air-conditioning system problem

[Bluesguy6]

Hello All, You were so quick to diagnose my last problem with my fridge that I thought I would see if anyone had a suggestion on my furnace/air-conditioning system problem. My front zone works but the rear does not. My fan won’t chance speeds, essentially always blowing on low. The furnace blows hot air fine and it heats the coach. The air also works fine, but again there is no ability to change speeds or program the rear zone. Any suggestions on where to look first, thermostat, control board or relays? I have an Atwood 8500 furnace, and the squirrel cages work fine too. The thermostat turn on, however not all functions work., i.e., can't program rear zone. In furnace mode you can not change speeds, although it says it changes speeds in some cases, it still does not change speds.
Thanks again for the previous help!

[RVhauler]

Replacement stat that was installed in my kountryaire has an additional zone which isn't hooked up to anything. My guess either your stat or board is fautly. Stats must be matched to board in order to work.

[Bluesguy6]

My major problem was that I couldn't program my zone 2 so i could get heat in the bedroom, however the AC worked fine. Also, no change in speed for the furnace. So I took a chance and got a new thermostat to try. I plugged it in and I just get "EE" on the display, and I can't make any changes, i.e. mode, temp zone. When I plug in the old thermostat I get back to where I was before and at least some things work. Is there something that has to be done with the thermostat upon installation, or do you think I may have a control board problem?
Thanks again for the help!
__________________

[Rex]

If you have a 4-button thermostat which is no longer available, and change it to a 5-button, you must then also change the control board in each roof air conditioner. Same cable from thermostat to AC and furnace is OK.

[Bluesguy6]

It looks like the thermostats are identical, they have the same circuit board number and both are 5 button thermostats, each has mode, fan, up,down and zone. It seems odd that the new would give me an error and the old one does not.

[Rex]

Try a system reset. If that does not work with the old stat, put the new one in and do the reset using it and see if that corrects the problem.


SYSTEM RESET

• Turn the ON/OFF switch to OFF position.
• Simultaneously depress and hold the MODE and ZONE push-buttons while turning the ON/OFF switch to ON. FF should appear in the LCD display until the MODE and ZONE push-buttons are released.

When a dip switch in the system control board is turned ON or OFF after initial configuration, a system reset will need to be done before the Comfort Control Center will recognize the updated selection.

[Bluesguy6]

Thanks for the info Rex! I will give it a try tonight and see if it does the trick. I suspect that the coach took some sort of a power hit before I bought it as the microwave display is also messed up. It functions, but it is difficult to read the display. That's my next fix after the heater/ac issue.