Honeywell CM927 users – seen this problem before?

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  • Honeywell CM927 users – seen this problem before?
  • Premier Icon Stoner

    Ive had about 4yrs faultless service from my two CM927 thermostats until the other day.

    Initially it would send a continuous call for heat signal to the relay. It did this for a few days before I noticed at which point I removed and reinstalled the batteries and it seemed to work for another 24-48hrs normally.

    Then the LCD went very faint/blank. Again I removed the batteries, tested for voltage supply from the batteries and reinstalled them. The screen returned to normal, but now the Room Temp is showing 39-42.5 degrees (!), all other functions and the screen contrast are working fine. I can not get it to show the correct room temp.

    I have removed the batteries and replaced with a fresh set and the problem remains. I have reset the user program to factory settings but that hasn’t solved anything.

    Anyone know if there is a software reset routine for it? I cant find one in the literature. Im guessing 4yrs is out of warranty, but surely you’d expect it to reasonably work for longer than that 🙁

    Ive emailed honeywell tech support – finger’s crossed they have a fix or a replacement for me.

    Premier Icon footflaps

    My professional diagnosis is that it’s ****.

    That will be £250+VAT.


    You’re doomed.

    Tech support = buy newer model.

    Is this the start of ‘what bodge repair for a wood burner….’ threads?

    Premier Icon Stoner

    I shall spite MrHoneywell by jerry-rigging a series of levers and pivots from my bedside to the central heating pump instead.

    More seriously, 4yrs out of a £125 controller? I will be having words with them I think.

    Premier Icon paulosoxo

    Is there a button cell battery as part of the controller?

    Premier Icon Stoner

    Good qu paulo! Hadn’t thought of that….
    Id need to open it up to find out as it’s not got it’s own battery compartment.

    Premier Icon Stoner

    Well, that’s a nope.
    pcb all looks fine, no burnouts, no oxidation. No reason not to work from visual inspection, I can only assume it’s something like a memory unit is not working properly 🙁

    Battery out for 2 hours hasnt fixed it, but it does remember time and date so it must have some long term no voltage memory.
    I wonder if it would clear if left with no battery for a week?

    Premier Icon Stoner

    It’s a 1 yr warranty and Honeywell dont want to know about it save for me buying another one.

    Fat chance.

    I used to recommend these but at £125 each with a risk of a three year lifespan, that’s not going to happen again. I’d rather run the risk of a a £30 chinese el-cheapo failing in the same length of time.

    What’s the point of paying premium for something with a UK/US brand if the company don’t back their own products? If I want to be left high and dry I can get the pleasure of a good reaming from eBay Hong Kong thankyouverymuch!

    And the same goes for the pile-of-crap Technoline weather stations.
    £110 for

    and the sender unit fails in <3yrs. They want another £40 for it – no discount, no warranty replacement. Stuff that! The remnants go on eBay and I will happily make do with a £10 inside/outside digital thermometer thank you.


    Not good , what do you all need to control ? Is the salus rt500 too simple for your needs – with all the different heat sources and zones/wings you have in the barn mines not looking pretty has been robust. If its even half as old as the heating system i removed then its had a good innings and id throw the same back in.

    Premier Icon phiiiiil

    I’m on my fourth weather station in four years (I think), and I just had to reset this one as it had lost sync with the outside bit for some reason. I don’t know whether I have some sort of affect on them (can you look at them too much?) or whether they’re all just a little bit cheap’n’nasty…

    We have a CM927 as well. Should I stock up on warm jumpers?


    Ive been using these Honeywells in my house for many years and put them in a house I rented out.

    When I sold the rental house I took it out with the aim to sell on ebay. I never got round to it.

    About 6 months ago the one in my current house just died ie the screen went. I put it down to it having been dropped by 3 yr old 2-3 times. However googling showed it was a common problem and Honeywell don’t give 2 hoots.

    Luckily I still have my old one which is now about 8 yes old and still working.

    If that one goes wouldn’t buy another. Unfortunately in the past i did recommend them here too.

    Might look at that British Gas smartphone app controlled one next…if they do a windows phone app version

    Premier Icon Stoner

    tt – I just need a wireless relay controller with a handful of day periods to set temp target. Doesnt need 7 or 5/2 day, just 1 day will do.

    I was thinking of one of those cheap Salus or the like. Im keeping an eye out on ebay.

    Fortunately I actually dont have much need of zone control in the barn. I have one to control the upsatird rad pump and one to control the downstairs UFH pump. When I finish walling in the boys toy room, then I will need one more controller and a handful of motorized zone valves though. They wont be Honeywell either. Bastards.

    Interesting to hear youve had same problems FD.

    phiiil – much as it was interesting to check windspeed and pressure, TBH it is external/internal temp that I use the most. I now have one of these

    Premier Icon ransos

    More seriously, 4yrs out of a £125 controller? I will be having words with them I think.

    That’s twice as long as you should expect from an On One carbon frame. 😉

    Premier Icon Stoner

    trail_rat, thanks for the pointer. Salus RF500 arrived from eBay this morning. £36 delivered.

    Easy swap, works fine. Plenty of range on the RF. And comes with a 2yr warranty whereas Honeywell only offer 1yr. And their stuff is patently shit at 3x the price.

    *puts Honeywell in the “Shit” column in his little notebook next to Celt sheepskin slippers and Technoline weather stations*



    I’ve just found this page by searching the net as I too have just found this week that the ‘room temp’ on my Honeywell CM927 is measuring 43.5 degrees!

    I contacted Honeywell and was told that this was not a known issue with the unit and it was suggested i remove the batteries and leave for approx 8 hours then re-insert the batteries. If this didn’t fix it then I would need a new unit!

    I did as they suggested but it made no difference.

    I’m presuming the unit is of no use anymore! I reckon I have had it about 3yrs….

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