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Regan Land
Regan Land, HVAC Technician
Category: HVAC
Satisfied Customers: 582
Experience:  18 years of experience, NATE Certified, Licensed HVAC Contractor, Certified IAQ Specialist
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Honeywell Chronotherm III. Has been flashing replace batteries

Resolved Question:

Honeywell Chronotherm III. Has been flashing "replace batteries" for a while. I ignored it thinking the batteries are only a backup. However, this morning display was dead and heat was off. I replaced batteries and now everything seems to be working fine. BUT . . . does this mean that the thermostat is not getting its power from the wires? And is it supposed to be? TIA.
Submitted: 7 years ago.
Category: HVAC
Expert:  Douglas replied 7 years ago.

You will want to look at the backplate (take thermostat off the subbase) is there a wire connected to C?

 

Also while you have it off, get the model number. It should start with a T, a CT, or some other letter followed by 4 numbers, a letter and more numbers.



Edited by Douglas on 3/17/2010 at 4:09 AM EST
Customer: replied 7 years ago.
Hello,

The model # XXXXX XXXXX

There is no wire connected to C. Actually there's not even a screw there, just a hole, Here is the wiring scheme from left to right:

O - screw but no wire
W - white wire
G - green wire
C - hole
R - red wire
R sub C - jumper to R
B - screw but no wire
Y - black wire

I have a gas furnace and central A/C.

So it's sounding like this is set up in such a way that it's normal for the controller to be running under battery power only?
Expert:  Regan Land replied 7 years ago.

Without a Common (C) hooked up, the thermostat will be primarily powered by the batteries. If you have an extra thermostat wire we can walk you through hooking it to the furnace and thermostat.

Regan Land, HVAC Technician
Category: HVAC
Satisfied Customers: 582
Experience: 18 years of experience, NATE Certified, Licensed HVAC Contractor, Certified IAQ Specialist
Regan Land and 3 other HVAC Specialists are ready to help you
Customer: replied 7 years ago.
Thanks, that's all I needed to know.
Expert:  Regan Land replied 7 years ago.
No problem, thank you for using JustAnswer!