Question about Honeywell Programmable Thermostat Heater

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Battery backup? I have a programmable Honeywell Thermostat T8000C or T8001C or T8011R. The thermostat has been working fine EXCEPT when I've lost power. I think there must be a battery backup to keep the time because the past month we've lost power twice and the thermostat gets completely lost and I have to reset the time. I've lived in this house for four years and not had this problem in the past. Is there an online site that will show me how to pull the cover off to find the battery? Also, do you know what battery I need to buy?

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Re: battery backup?

Which model do you have ? the 8000/8001 or 8011 the set is different depending on your type of heating system. This model has a memory chip not a battery that saves your settings. So you could be looking at replacing the unit.

Posted on Mar 08, 2008

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Re: battery backup? - Honeywell Programmable Thermostat Heater Thermostats

How do I change the battery on t800lc

Posted on Jul 19, 2011

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1 Answer

How do I change the battery on Honeywell Thermostat T8001C?

According to the manual for the model series (see link), only the T8002 Model has batteries. They are accessed from the right side of the thermostat. See page 14.

Jan 10, 2015 | Honeywell T8001C1019 Programmable...

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My Honeywell T8001C doesn't allow me to change the indefinite temperature hold for some reason

It sounds like the thermostat is malfunctioning; the Set should not be flashing at all, only the Hld should show after pushing the hold button.
Do you have a new battery in the unit? Is it set to Heat or Cool? Is it already programmed for current Time/Date and does it have a schedule programmed in already? If you've lost the user manual it's here:

Jul 06, 2014 | Honeywell Programmable Thermostat Heater

1 Answer

My Honeywell programmable thermostat's display is blank and I do not have any heat?

The thermostat, depending on the model, normally does not get powered by batteries, they are for backup power. You might be losing 24 volt from the furnace, causing the thermostat to run on batteries.

Apr 09, 2014 | Honeywell Programmable Thermostat Heater

1 Answer

I have Honeywell T8011R programmable Thermostat. Turn AC on last night for first time...working fine...came back late morning to find display and fan off. Check circuit breaker...on. I took it off and...

Hello, first you must verify if you are getting 24 volts to the tstat at the secondary side of the transformer, if not you have a bad transformer. If you are getting 24 volts then check the batteries in the thermostat.

Apr 12, 2011 | Honeywell Programmable Thermostat Heater

1 Answer

T8011r thermostat doesnt have a display, fuse is not blown out and it suddenly stopped working

Here is a link for the owner's manual. It gives several suggestions for the cause of the display being blank. Check those and let me know if that helps.

Jun 06, 2010 | Honeywell Programmable Thermostat Heater

1 Answer

Have the honeywell t8001c thermostat - no batteries - it holds the programming fine but not the date/time - what to do?

Go to
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions
If you can’t find what you want, the bottom left and bottom of web
Page, they have homeowners assistance and Home products to get the help you need.

Mar 06, 2010 | Honeywell Programmable Thermostat Heater

2 Answers

Honeywell T8011R

Check for either an in-line fuse in the heating unit or a fuse on the control board also in the heating unit.

Nov 06, 2008 | Honeywell Programmable Thermostat Heater

2 Answers


I have a Honeywell Programmable Thermostat, T8011R. The users guide for the T8000 series can be found at:

To keep your temperature at a single setting, just enter the temperature at every period, i.e. WAKE, LEAVE, RETURN AND SLEEP for both the Monday through Friday time frame and the same for the weekend. I do this at 55 degrees when I'm going to be out of town.
To 'Guest' , enter your 68 degrees at WAKE, LEAVE and RETURN, then enter 66 degrees at SLEEP. Do this for the Monday through Friday time frame and again for the Saturday - Sunday time frame.

Dec 19, 2007 | Honeywell Programmable Thermostat Heater

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