Question about Honeywell Electronic Programmable Heat/Cool Thermostat - CT3300A100 Heater

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Honeywell UtilityPRO thermostat backlight won't go off

The green backlight on one of my brand new Honeywell UtilityPRO thermostats won't go off -- it goes dim, but not off, so we have this green glow in our room all the time. My other brand new UtilityPRO thermostat is fine -- a couple of seconds of inactivity, and the light goes off. There's no code 280 in the advanced functions... any ideas on how to set the backlight?

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  • scarobinson Jul 19, 2009

    I don't have an obvious model # -they were installed by our utility company. The bar code on the operators manual is 85-3126, and the bar code on the thermostats is 443045388, if that helps. The only other identifying mark is the name: UtilityPRO series, "Touchscreen Programmable Demand Control Thermostat." It's one the utilities install so they can cycle your A/C on and off during periods of peak demand. Trying to be environmentally friendly here, but now have a green light glaring at me 24/7!



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After posting that I was having the same problem, I found a solution.
I used these instructions and followed the Installer Setup on pages 6 through 10. Basically you just need to enter the setup mode following the instructions, scroll to setting# 280 and change the setting from "1" to "0" then the backlight will turn off after 8 seconds. Don't change any other settings if you don't know what you are doing.

If you need further help, I’m available over the phone at

Posted on Jul 24, 2009

  • theboop4u Dec 19, 2010

    This worked for me. I was initially told by my utility company installer that if I wanted to change the backlight option later on, I would need to call them for instructions since the code was not included (instructions manual stated to press one middle button that only gave limited codes). These instructions worked perfect.

  • nurahsmith
    nurahsmith Oct 29, 2012

    I would really like to thank you for posting this response. I've been living in my home for nearly five months and that backlight was driving bonkers. Thanks again.


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Do you have a model # for that stat? I can probably get the setup manual for you that shows how to disable\adjust the backlight function.

Posted on Jul 18, 2009

  • Mike McDowell Jul 20, 2009


    I think you have a bad stat because the backlighting is not adjustable. I do have the owners manual that I can send you just send me an email @ and I'll send it to you.



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The UtilityPRO program is described here:

and the manual for 85-3126 is linked at the bottom of the page. The instructions for the backlight are on page 22.

Posted on Dec 04, 2010

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It is how they wired the unit. If it is wired to run on 24 volt it is on all the time if it is on 12 v it shuts off as it derives power from the battery. You have last years model.

Posted on Jul 01, 2010

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