Honeywell CM67 Thermostat

[bbuk]

Hi - I've got a Honeywell CM67, and no matter what setting I put it on, Manual, Auto, off etc, the heating seems to come on whenever it wants. Nearly all the time. Has anyone any ideas what I can do?

 

[D_Hailsham]

It may not be the CM67 causing the problem.

Are there any lights showing on the receiver when the CM67 is set to off?

 

[bbuk]

I'm not entirely sure where the receiver is? Is it wireless? The CM67 is on the wall and it has wires going through the wall....

 

[Blagard]

Hi - I've got a Honeywell CM67, and no matter what setting I put it on, Manual, Auto, off etc, the heating seems to come on whenever it wants. Nearly all the time. Has anyone any ideas what I can do?

Has it ever worked as intended, or is this a new installation?

 

[bbuk]

Yes it has worked - its been fitted for 6 years. I've just taken the CM67 off the wall and the wires behind are just a power supply. So it must be wireless. Will the receiver be behind the cover of the boiler?

 

[Blagard]

Your CM67 is a hard wired device so no receiver.

It does sound as if it is not working properly any more and may need replacement (It is discontinued).

You could try setting it back to factory defaults which is at the bottom of the parameter list in the document linked below.

http://www.honeywelluk.com/Documents/Installation-Guide/pdf/1020.pdf

Edit:
Correction, just two wires and earth. Try changing the batteries

 

[bbuk]

Thanks for your advice, I will try that.

 

[Blagard]

Please see my correction above about how many wires I would expect to see

 

[bbuk]

Theres only two wires behind it.

 

[dreadnoughtheating]

I reckon 'optimisation' is on….

try this

TURN OFF “OPTIMUM START” CM67

STEP 1 PUT THE BOTTOM LEFT-HAND SLIDER IN THE OFF POSITION

STEP 2 PRESS 3 BUTTONS TOGETHER (at exactly the same time) WHICH ARE:-
THE INFORMATION i BUTTON AND PROGRAM BUTTONS 3 & 4
This will show a code of:- ICL 1 – let go of buttons

STEP 3 PRESS PROGRAM BUTTON 2 This will now show a code of 3OT 1

STEP 4 PRESS THE + BUTTON (on the left-hand side of the digital display) TAP THROUGH UNTIL YOU REACH 15 OP 1

STEP 5 WITH THE TEMPERATURE DOWN BUTTON CHANGE THE 01 TO A FLASHING 0. CONFIRM THE FLASHING 0 WITH THE INFORMATION BUTTON i The 0 will now be static

STEP 6 PUT THE THERMOSTAT BACK IN TO THE AUTO POSITION. THE “OPTIMUM START” IS NOW SWITCHED OFF

Do, please let us know if this helps.

DH

 

[bbuk]

The Code inside the CM67 is T6667B1069 - there is a * which says "optimisation not available on T6667B1069" - I have gone through as you said earlier and reset to factory settings. I've just put brand new batteries in it as well. So hopefully this is going to work. Its still a balmy 26.5 degrees in here!

 

[D_Hailsham]

Your CM67 is a hard wired device so no receiver.

I was thinking of the CM67RF.

 

[PK2022]

Hoping someone can help here please, and appreciate that this thread is aged/closed a long time ago!

We have similar issue with our CM67 NG
Has a total mind of its own in that Auto doesn't seem to work and when putting on Manual, the gas icon shows, you briefly see the wireless icon flash, but nothing happens for hours. Then the heating will kick in and burns like hell. Can't regulate anything. If left on Auto it will do zero for days, the thermostat says house temperature is 14 or 15 if not cooler (we are in a cold snap) even though we have the stat set to 20.

Likewise with Manual, we switch it to manual and nothing happens, despite cranking the temp to 30, nothing reacts and then in the middle of the night it is a furnace.

Have tried resetting the unit (putting batteries in wrong, waiting 10 seconds etc) and replacing everything and also turning off the Optimal settiing.

Worked fine previosuly for 10 years and not messed with it but no idea what it is.
Can anyone help please, thank you!

 

[dreadnoughtheating]

Is the relay / receiver unit giving a green light when the flame icon appears?

If not check out any YouTube video on how to test wireless signal strength and /or how to ‘rebind’ the two Honeywell components.

If you do get the green light going onwhen demand is called for and then off when you do not want heat the issue may be further into the wiring of the rest of the system.

 

[PK2022]

Sorry, should have also added that I have rebinded them.

In manual mode, when the wireless icon flashes, the green light on the receiver does come on and stays on for about 30 seconds.

The green burn light on the boiler (Worcester) will also come on, but then goes off too.

Also taken the thermostat off the wall and looked for any sign of dust / debris in it. Really can't think of anything else I can do, thank you.