If I replace CM927 will it work with the existing Relay box?

nichosi · Jan 12, 2020

Hi.
CM927 Wireless programmable Thermostat and Relay box were fitet in my house Sept. 2008.

Now the CM927 seems to misbehave, If I buy a replacement CM927 will it work with the existing Relay box?

SimonG · Jan 12, 2020

By relay box I take it you mean receiver?

I would just by a new set.

Chuck · Jan 12, 2020

nichosi said:
If I buy a replacement CM927 will it work with the existing Relay box?

Before buying a replacement... Have you reset the pairing ('binding') of the existing devices and installed new good quality batteries in the CM927? (By 'good quality' I don't mean some fake you got cheap from eBay but branded, e.g. Duracell, and bought from an authorised stockist with a big turnover, such as a supermarket.)

I would expect the new device to bind to the existing receiver without any trouble but personally I'd buy the pair because the cost won't be much more if you hunt around a bit and it won't hurt to have a spare 'in stock' if it's not needed.

nichosi · Jan 12, 2020

Chuck said:
Before buying a replacement... Have you reset the pairing ('binding') of the existing devices and installed new good quality batteries in the CM927? (By 'good quality' I don't mean some fake you got cheap from eBay but branded, e.g. Duracell, and bought from an authorised stockist with a big turnover, such as a supermarket.)

I would expect the new device to bind to the existing receiver without any trouble but personally I'd buy the pair because the cost won't be much more if you hunt around a bit and it won't hurt to have a spare 'in stock' if it's not needed.

Thank you

Yes the good bats are 3-4 months old & show still charged on the mustimeter.

It must have been paired by Mark the plumber on installation Sep. 2008

Can I reset the "pairing" & how?

What happened 3 days ago, in AUTO (always used auto) it failed to heat (cold rads), & now every time we have to give it a nudge by increasing the demand Temp 1-2 degrees from 29 (Ambien room Temp 19 dc) & it starts heating again, & also 3 midnights ago it came ON on its own when its programmed to go off at 10:00.

Chuck · Jan 13, 2020

nichosi said:
What happened 3 days ago, in AUTO (always used auto) it failed to heat (cold rads), & now every time we have to give it a nudge by increasing the demand Temp 1-2 degrees from 29 (Ambien room Temp 19 dc) & it starts heating again, & also 3 midnights ago it came ON on its own when its programmed to go off at 10:00.

Okay, I'd say those are the symptoms of a CM927 problem not a communication ('pairing') problem.

You could try performing a 'factory reset':

https://ensupport.getconnected.honeywellhome.com/s/article/Can-I-perform-a-factory-reset-on-CM921-and-CM927-Programmable-Thermostat?language=en_US

and reprogramming your cm927 but the chances of it fixing the problem are slim to zero.

In your position I'd just order a replacement. The only way to be sure with these problems is to test by substitution.

nichosi · Jan 14, 2020

Chuck said:
Okay, I'd say those are the symptoms of a CM927 problem not a communication ('pairing') problem.

You could try performing a 'factory reset':

https://ensupport.getconnected.honeywellhome.com/s/article/Can-I-perform-a-factory-reset-on-CM921-and-CM927-Programmable-Thermostat?language=en_US

and reprogramming your cm927 but the chances of it fixing the problem are slim to zero.

In your position I'd just order a replacement. The only way to be sure with these problems is to test by substitution.

Thank you Sir, I will act immetiately. …..nick

Magic · Jul 9, 2020

Hi, wondered how you got on with this? I have the CM927 like yours installed about 10 years ago with the receiver box. Seems it has done rather well as the screen has been okay but the 'up' button has been becoming less and less responsive and thought I would be organised and sort over the summer. Quote for a new (upgraded) model was around £170 and being on a tight budget I bought a replacement unit (Just the thermostat) from ebay. I read the instructions first thinking I just needed to unbind the current one and rebind the new one however it has turned out not to be so simple! When I press the button on the receiver it does the right flashing sequence but when I press the combination on the thermostat (up, down and left) it doesn't display ' InSt and CONTROL BINDING' as per the instructions. I thought I had bought a faulty product but when I tried to rebind my original thermostat that wouldn't display what it is supposed to either.

Has anybody come across this problem? Maybe I have to accept I need to have a new receiver and thermostat installed but I just wanted to find out what the problem is with mine first!

Many thanks in advance for any advice,

maxwell · Oct 30, 2021

Hi just wondering what the outcome on this was? I too have a Honeywell CM927 and the screen is not displaying the numbers correctly anymore and difficult to read what the display is actually showing.

Can I buy a compatible unit that would work with the existing receiver or do I need to buy a combo (unit + receiver)?

Appreciate any feedback on this

Rikard · Feb 23, 2023

maxwell said:
Hi just wondering what the outcome on this was? I too have a Honeywell CM927 and the screen is not displaying the numbers correctly anymore and difficult to read what the display is actually showing.

Can I buy a compatible unit that would work with the existing receiver or do I need to buy a combo (unit + receiver)?

Appreciate any feedback on this

Interesting, the up button on our CM927 unit (the remote wifi bit) has become less and less responsive and now I can only turn the temperature down which is good for reducing gas bill but I'd prefer for the unit to work as intended. There are also some issues with the screen flickering but doesnt seem to be battery related but having read thread above I might get some new ones as a douible check. The other issue I'm having is that with hot water not coming on when the room thermostat thinks the boiler should be off so i'm having to disable the central heating in order to haver the hot water coming on. Very odd.