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JamesI, Handyman
Category: Appliance
Satisfied Customers: 2154
Experience:  I have repaired and maintained numerous items over the years, from fridges to freezers, radios to TV's.
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My daughter has a Honeywell CM921 digital room thermostat.

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My daughter has a Honeywell CM921 digital room thermostat. Her problem is that neither the timing button (+ or -) nor the temperature button (+ or -) are responding in any way, consequently she cannot turn the heating on albeit she does have hot water. When she presses these buttons nothing happens ie nothing appears on screen. New batteries have been installed and the screen is 'live' with other information. Can you advise please.
Thank you.
***** *****e

Hi Brian,

This is most likely a hardware fault in the thermostat itself, as a consumer the only two things I can suggest are.

  1. Check if any buttons have become stuck pushed in (such as the OK button), as that would stop it picking up the press of the + and - buttons.
  2. Remove the batteries, and inside the battery compartment, just above where the batteries sit are two small clips, push those in with a lot screw driver, and then, pull the bottom of the thermostat towards you, this should lift it off the bracket on the wall. Give it 10 minutes then place it back, secure the top first, then pushing the bottom into place. This affectingly resets the unit and should clear the memory, should it have been due to a software fault.

If the fault still occurs I would suggest you look to replace the CM921, as found by following step 2, its just a clip off and clip back on, there isnt any wiring required. The cheapest I have seen a new unit was for £95 here on ebay, but if your looking for one today you can pick it up here at Screw Fix for £118.

Please let me know how you get on.

I haven't heard from you in the last few days, please let me know if you need any further assistance, if not I would appreciate if you could rate the service received.Many thanks
I havent heard from you in a few days, and wanted to understand if I can be of any further assistance?



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Customer: replied 1 year ago.
Hello Jamessorry for slight delay in responding to your answer. Have tried both your suggestions, regretably without success and I conclude that the thermostat's software has developed a fault necessitating replacement..RegardsBrian