Having issues with my thermostat

[Isaac-1]

NO YOU DO NOT!!!

These modern Hunter and Honeywell thermostats run on a pair of AA batteries, they don't care about the 7.5V power supply, in fact if you look at the wiring diagrams in the links above the 7.5V supply line is not even connected.

Now this will only work on the Dometic "Analog" style units, not the newer models which use a modular phone jack style connection

 

[NY_Dutch]

As Isaac said, "NO YOU DO NOT!!!" The only difference in what he said is that our two Honeywell RTH2510B 7-day programmable t-stats use AAA batteries instead of AA's.

 

[Bobtop46]

Nice, good to know. Thanks for the update.    )

 

[NY_Dutch]

I change the batteries annually on New Years Day. I'm sure they'll last a longer than that, but I think it's cheap insurance.

 

[kjansen]

Old thread but applies.  I just bought the newer numbered replacement and when now when I turn the furnace on, I only get A/C running no furnace.  A/c runs also when set on A/C.  Is there a fuse some place on the furnace itself?

 

[NY_Dutch]

Have you compared the new thermostat wiring diagram to the old one to see if there's a difference?

 

[Ernie n Tara]

Are you sure you don't have a heat pump? Mine will rely on the AC in heat pump mode until the lag in temperature exceeds four degrees. e g set for 70 deg F and actual is 67 I get only the heat pump.

Ernie

 

[Gary RV_Wizard]

I just bought the newer numbered replacement and when now when I turn the furnace on, I only get A/C running no furnace.

Replacement thermostat or replacement furnace or a/c?    Please tell us specifically what the old model number was as well as the new one. Then maybe we can figure out what is happening.

The thermostat "heat required" signal can go direct to the furnace or pass through the a/c zone controller. It will always do the latter if the a/c is a heat pump or if there are multiple heat/cool zones.

The furnace itself doesn't know or care where the signal comes from - it just waits to sense +12v on the "heat required" signal line. It has its own separate 12v power (which is fused). You can check for power at the furnace whether it is running or not - there should always be 12v to the furnace circuit board.