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Matthew
Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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Hello; I have a Honeywell TH4110D1007 programmable thermostat. It

Customer Question

Hello;
I have a Honeywell TH4110D1007 programmable thermostat.
It stopped working correctly.
The thermometer reads 10 degrees lower than the actual air temperature, My heater runs constantly, stopping for 2-3 seconds then turning on again.
The unit lights up to pushing the buttons. The temperature setting moves up & down accordingly. I can turn the heater on & off by moving the on & off sliding switch.
Do I need to replace the thermostat, or is there a way to recalibrate the thermometer to make it accurate again?
Submitted: 6 years ago.
Category: HVAC
Expert:  Matthew replied 6 years ago.

Matthew :

Hello, My name is XXXXX XXXXX I will do my best to help you today.

JACUSTOMER-8gwxskgu- :

great

Matthew :

If the ambient temperature on the stat(the one telling you what the temperature inside the house is) seems to be dropping and not coming up to meet the demand temperature you set it at then you have a furnace problem not a thermostat problem

Matthew :

When you turn the thermostat to heat and turn the setting up beyond the ambient temperature does the system come on and blow heat?

JACUSTOMER-8gwxskgu- :

OK. I am confused because my other honey thermostat on the other side of the house reaches the set temperature and runs correctly.

JACUSTOMER-8gwxskgu- :

What now? Call an HVAC technician to the house?

Matthew :

Do you have a zone system where both these thermostats run the same furnace?

Matthew :

or do you have a furnace for each thermostat?

JACUSTOMER-8gwxskgu- :

Good point. 2 different furnaces, 2 different thermostats.

Matthew :

okay. if you like we can see if it is something simple

JACUSTOMER-8gwxskgu- :

go ahead

Matthew :

I just need you to go to the furnace and tell me what it is doing. A model number on the furnace would be helpful as well

Matthew :

Is this gas?

JACUSTOMER-8gwxskgu- :

yes gas. going up to attic to check

Matthew :

What I need you to do is turn the thermostat to heat then turn the temperature up. Go to the furnace and take both doors of the furnace off. When you take the bottom door of the furnace off this disengages the door safety switch and cuts power to the unit. With your finger hold the door safety switch in and observe what the furnace does or doesn't do in this sequence.

JACUSTOMER-8gwxskgu- :

Soory.

Matthew :

Inducer draft motor comes on(small one hooked to the exhaust pipe), pressure switch pulls in, igniter energizes, burners come on, flame is sensed, blower comes on.

JACUSTOMER-8gwxskgu- :

I am going to have to disagree with you. WHen I remove the thermostat unit from the wall, the temperature indicator on the thermostat is all over the place, A different ambient thermometer in the same location registers 10 degrees lower or hiigher than the thermostat

Matthew :

The number on the left is jumping all over? not staying on a set temperature?

JACUSTOMER-8gwxskgu- :

That is correct. I am in a different room with the thermostat AND had a diferent ambient thermometer that is accurate and the thermostat thermometer now reads 5 degrees higher thant the actual ambient temp.

JACUSTOMER-8gwxskgu- :

I appreciate your time and effort. I will hit the ACCEPT button. I need to head to work. I will work on this late. THanks for the time and effort.

Matthew :

It coudl be the internal thermostat is bad but if the setting on the right is higher than the setting on the left the furnace still should come on regardless of that fact that the setting on the left is right or wrong all the thermsotat knows is that you want it warmer than what it says.

Matthew and 2 other HVAC Specialists are ready to help you
Expert:  Matthew replied 6 years ago.
Try taking the thermostat off the wall and take the batteries out for 5 mins and see if it resets the internal settings. Sometimes this helps with sporadic operation.

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