[Tom Henry]

Hi.... I've got a Carrier hvac system. It was installed in 2010 so fairly new.

They company installed a Honeywell TH6110 programmable thermostat and up until about three weeks ago performed flawlessly. Now it's intermittent.

Sometimes it will work fine and other times will not turn on at setting. Right now it's set for 69 on a temporary setting and it is dropping below to 63 without turning on. It won't come on even if I raise it to 72. But then, a half hour later will work fine.

Anyone else hear of this?

Thanks in advance. Tom

 

[jagans]

Hi Tom,

Does this take batteries? If not I would suspect dirty contacts, or a bad transformer?

 

[jagans]

Hi Tom,

Does this take batteries? If not I would suspect dirty contacts, or maybe a bad transformer?

 

[Tom Henry]

Yes. I have put in fresh Duracells in

 

[sammy37]

Usually a transformer just quits and never works again. The problem may indeed be the thermostat but it could also be a problem with the furnace.
Since this is a fairly new install, I would have the installer come out and check it but if you wanted to, next time it acts up, remove the thermostat and run a jumper between R and W and see if the furnace starts.

 

[sammy37]

When you raise the thermostat above the room temp, do you hear it click? If yes, than its usually pretty safe to say that the thermostat is working and the furnace would be suspect.

 

[Tom Henry]

I had the installer on call and found out it was $99 for the service call and the first half hour. They couldn't come until tomorrow. Seeing that this not a dead hvac or something that is an emergency, I told them no thanks for now.

I didn't hear a click when raising the temp. When I set it to just fan, it would come on. when I turned it back to auto, the fan stopped.

But I did pull the thermostat off the wall to check the wiring. Everything looked in order and after I snapped the thermostat back in place, I adjusted the temp upwards and the furnace started heating.

Could it be a dirty contact?

 

[jagans]

Yup, it sure could. CRC QD Electronic spray at your local WalMart. I even use it for starting fluid! :jester:

 

[Tom Henry]

Thanks. I'll try it and report back.

 

[jagans]

Sounds like you already fixed it. Just the friction between dirty contacts can clean them enough to complete the circuit, and you probably had marginal batteries.

 

[Tom Henry]

Well...... as it happens.... not all things are as they appear.

After more issues with the thermostat not keeping the temp near the setting, I replaced it with a new one.

I got lucky and found a compatible Honeywell model and it was easy to change even though I had to change the base plate.

Thanks for your help sammy37 and jagans. :thumbup: