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Tim Cooke
Tim Cooke,
Category: HVAC
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Experience:  Owner at Self-employed
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I'm trying to replace a Honeywell CM907 thermostat, screen

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Hello, I'm trying to replace a Honeywell CM907 thermostat, screen went blank. Seen one on eBay 'thermostat only' but the seller asked - Hi do you have someone to pair the thermostat with the heat link attached to your boiler? I’ve been told that the heat link and thermostat come paired together in the box and if you separate them They need manual pairing. Is this ok? Can you advise if I should buy this. Thanks very much. Fiona
JA: Have you replaced your Honeywell thermostat or parts of it before? If so, how long ago?
Customer: No, it's seven years old and never been replaced, just stopped displaying so no timing or temp control.
JA: What have you tried so far with your Honeywell thermostat?
Customer: The plumber has suggested replacing it with new wired version but at the moment just trying to replace the thermostat, the boiler is still working
JA: Anything else we should know to help you best?
Customer: Just to answer my original question. Is it worth buying a used thermostat that matches but might need manual pairing. It's the technical question I need help with please.

Hello, the CM907 is a wired thermostat, not wireless, so you won't need to pair it.

Have you checked the batteries? It could simply be that they need to be replaced.

Customer: replied 6 months ago.
Hello Tim, we tried 3 different new batteries. The screen has gone blank, no control of timing or temperature, boiler is fine. So the seller's question to me doesn't apply to this? He is just selling the used thermostat he has replaced, they don't make CM907 anymore. Will it an straightforward replacement. Thanks

The nearest equivalent to the CM907 is the ST9100C. There's also a T4, which has Honeywell's newer look and a different style of user interface.

I wouldn't buy any secondhand thermostat, and I probably wouldn't buy any thermostat on eBay. Screwfix sell the above two that I mentioned, if you struggle to find a good plumbers' merchant.

You can install a wireless thermostat but they're more expensive and, again, I wouldn't buy on eBay. The nearest equivalent wireless stat is the CM927.

Tim Cooke and other HVAC Specialists are ready to help you
Customer: replied 6 months ago.
Ok, Thanks for your advice and help. Fiona