Friday 6 October 2017

Honeywell CMT927 LCD Display Problems

Main problem: LCD Display Fault. The Honeywell CM927 (CMT927A1049) Wireless Chronotherm Thermostat sits in a higher price bracket than many of its fellow, same brand thermostats. Overall, Honeywell do make great products. They've been in the business for many years and the big majority of their products are very reliable. However, there are some that slip through the net. Sadly, this model is one of them, and as a result, does not have the best reputation with customers. This is mainly due to problems with the display. Which, unfortunately, is not the only Honeywell model to suffer from a very similar issue. The CM907 is also cursed with screen problems. So what exactly is the problem? Well, the LCD screen issues come in many forms.

Fading, jumbled up letters and numbers, partly dead, and total failure. There is also no set time for if / when this happens. It can start to play-up after a few months, or, more commonly, after several years. It should be noted that not all CM927's suffer from issues. Many are just fine, with no issues to report. But, there are a considerable amount of complaints, which translates to many failures overall, and for a thermostat with a high price tag like this, it is a real disappointment. We're not talking about a twenty pound unit here, the CM927 costs over £100 to buy brand new.

The main culprit for the screen failing is moisture getting inside the control unit over a random period of time, causing the gradual development of the screen becoming unreadable / dying. And with this it goes without saying. Unreadable equals the inability to actually operate / program the thermostat, leaving it pretty much useless.

How To Fix It?

There are various methods out there. Some people have put their whole unit in the oven on a low gas mark in an attempt to dry it out. This is not recommended! Others have taken the LCD screen out (quite straight forward) and used either a hairdryer or toaster to heat it up. This method really does work and is the recommended "do-it-yourself" for a quick repair. See the video for exactly how to perform this repair by Handy Hawkins below. He is doing the repair on the CM901, but it also works with the CM927, CM907 and others.


However, most have tried placing it in an air tight bag with silica sachets in an attempt to remove any moisture. Sometimes these methods do work well and the thermostat is fixed well enough to be operated. The success rate is high. How long it stays fixed for though is another matter all together.

These fixes are usually temporary, not permanent. But if one of the methods does fix your LCD, and then after a few months it develops the same problem again, just try the same trick that sorted it out the first time. There's a very good chance it will work again. Saving you the cost of a replacement. In some cases you might not need to take the unit apart.

If you don't feel comfortable taking the display out, you can always apply some gradual, light heat to the front of the LCD screen. Apply clamps or light pressure of some kind. Use a hairdryer, heat gun or toaster and steadily wave the heat on to the display. Once the display darkens a little, test it out. Rinse and repeat if the first attempt doesn't have the desired effect. If all else fails, bite the bullet and open it up. It's not hard to do, as most pieces just clip in / out. Follow the hairdryer / toaster technique and get it up and running again.

I'm no DIYer, I Want My Money Back

Honeywell are well aware of this problem. I'm not sure on the exact time-frame, but if your CM927 (CMT927A1049) fails within a couple or more years, Honeywell should refund you or send a replacement free of charge. Depending on how long Honeywell offer on this thermostat, check whether it is still under warranty. Dig out your receipt if you have one, and take some pictures showing the fault and they should offer you one of the two options above.

If you don't have the receipt, it doesn't necessarily mean all is lost. There should be something on the unit itself which confirms its age / date of issue / manufacture. This should determine whether your CM927 falls within an acceptable time frame (pretty sure its around five years) to justify Honeywell giving you a refund or replacement.

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26 Comments:

At 6 October 2017 at 21:13 , Anonymous Noon said...

Great Post. Personally what I would do is dry out the screen and test so it is working again. Then while the plastics is off, fit mini silica bags inside. If the curcuit board is making it a tight fit (there should be loads of room for those little silica satchets), tape them to the inside of the plastic housing (same side where the LCD is located) and screw it all back together.

Get them as close to the LCD screen as possible. This way any future moisture build up stands a good chance of being partly eliminated. Repair after thought to make monies... Buy all the no-display ones repair them and sell for good profits. happy days Tee hee.

 
At 15 October 2018 at 06:51 , Anonymous Pangers said...

Genius post! Just followed the video and used a hair-dryer. Worked perfectly! Thank you!

 
At 26 July 2019 at 07:57 , Blogger Unknown said...

After 10 years of excellent service CMT927, I too now have a faulty display. On reading the possible fixes I opted to take it apart and if it didn't work then just get a new one although they are expensive. It's not easy to dismantle but with patience and basic logic it all un-clips and then goes back together and to my delight the hair dryer method worked fine for me its now a week later and still going fine. Better still I've saved myself well over £100.
Thank you for your ideas.

 
At 30 August 2019 at 09:54 , Blogger Unknown said...

I have the same problem and have had it before. It seems to go wrong during the summer months when it is switched off.

 
At 12 September 2019 at 13:07 , Anonymous Anonymous said...

I’ve used this twice now, thanks very much for posting :)

 
At 10 October 2019 at 16:00 , Blogger nononsens said...

Please do not believe this nonsense! It wil last some weeks or months but the problem will come back and worse as before! There is only one good solution, see " a better way to repair your honeywell ".

 
At 7 August 2020 at 05:01 , Anonymous Anonymous said...

Great post from 2017

So, it's August 2020 now and approaching the end of lockdown in UK and the thermo-thingy went wonky... found this post in a simple search and I've fixed it... saved me £120 if it works permanently, but otherwise, just the thrill of getting it working was worth it!! Don't usually post on these places, but hey... it works!!!!!!!!!!

Thanks!!!

Nigel
CARDIFF UK

 
At 23 August 2020 at 03:55 , Blogger Unknown said...

I have two CM907s, and both failed gradually years ago. They eventually really annoyed me so I though why not give it a go. It worked a treat on the first one, and will now do the second. You need no tools or intelligence to do this fix. Genius posting, and saved me £200. Thanks

 
At 27 August 2020 at 07:47 , Blogger Unknown said...

Excellent post. UK, Aug 2020, and the end of the good weather. Ours has been faulty for several months now and, when a I saw the price of a new one, thought it about time I had a look at a repair, 5 underneath a hairdryer did the trick. Thanks very much.

 
At 11 September 2020 at 09:41 , Blogger Sarah said...

Did the diy route! It worked a treat! Thank you.

 
At 25 September 2020 at 00:59 , Anonymous Hussain said...

Worked a treat. Legend.

 
At 26 September 2020 at 06:28 , Anonymous Anonymous said...

Followed the video - worked a treat and saved over £100. Thank you!

 
At 30 September 2020 at 00:43 , Anonymous Anonymous said...

I too have tried this and it worked for a while, but has now lost its digits again, so I contacted Honeywell but can't get anywhere unless I can find the receipt .. now I have to replace it I will use anyone except Honeywell

 
At 9 October 2020 at 15:53 , Anonymous Anonymous said...

Many thanks for the advice. It worked a treat on my CM927, after 2 minutes over the toaster and cleaning of the contact strip for the screen on the circuit board.

 
At 31 December 2020 at 04:36 , Anonymous Mark Leigh said...

Followed this video nervously convinced I couldn’t do it! Took pictures every step of the way so that I knew how to put it back together again. Used a hair dryer over front, rear and sides of the display unit once detached. Couldn’t believe the result! Now works perfectly, clear display, all digits showing, good as new. Thank you for such a helpful informative easy to follow video. Mark

 
At 31 December 2020 at 04:57 , Anonymous Mark Leigh said...

Followed this video nervously convinced I couldn’t do it! Took pictures every step of the way so that I knew how to put it back together again. Used a hair dryer over front, rear and sides of the display unit once detached. Couldn’t believe the result! Now works perfectly, clear display, all digits showing, good as new. Thank you for such a helpful informative easy to follow video. Mark

 
At 12 February 2021 at 03:26 , Blogger Floxxie said...

I just used a hairdryer blowing on the back of the unit for less than 2 minutes... looking good!!

 
At 5 March 2021 at 02:10 , Anonymous Anonymous said...

I also went with the hairdryer over the front and a careful squeeze. Result!

 
At 29 July 2021 at 06:33 , Anonymous fayenatic said...

This worked for me last year, but today when I tried this again twice (using a hair dryer for about a minute rather than a toaster), it left the display worse than before. Then I followed a hint at DIYFAQ and held it at one end, heated it at the top edge where the plastic ribbon connector is, and then clipped only that edge for a couple of minutes. Wow! The display is completely restored, for now.

 
At 23 August 2021 at 00:14 , Blogger Unknown said...

I am not that good to take it apart but will try hair dryer on screen and back of device as this happened last summer after I had turned off heating, come autumn can't read anything...

 
At 2 September 2021 at 08:31 , Anonymous Anonymous said...

I first tried by heating with hairdryer for about 1-2min. Reassembled it. It didn't work.
I retried the process, this time heating it up to 4min + soft press on the screen.
Reassembled and it worked perfect now.
Thank you to the poster and the video demo.

 
At 30 September 2021 at 05:20 , Blogger Unknown said...

I million thanks. It has worked for both of my controllers. The only adjustment, that I needed to heat the LCD for a minute (maybe due to the toaster heat) and had to repeat the process twice on 1st, and 3 times on the 2nd device. BTW - it was done in Hungary

 
At 30 September 2021 at 05:31 , Blogger Unknown said...

It has worked for me for 2 controllers. I needed more than 20 second for the heating (cca. 1 minute) and had to repeat it 2-3 times. Also after 2-3 years needed to repeat the whole process as the display has become ilegible. BTW - it works abroad as well
Attila the Hun

 
At 1 October 2021 at 04:03 , Blogger C.Levey said...

Tried the toaster method 1st, and it made it worse the first time. Gave a 2nd heat. Still poor display. Then tried the hairdryer method. After 2nd attempt all good. Did take a bit longer than the 20 secs, probably a couple of mins. I noted the comment about applying heat to the taped contact strip on the edge. The display got dark enough to just make out all of the digits on the display. Then after returning to the unit, is working perfectly again. Many thanks for the video, and saving me the cost of a replacement!!

 
At 11 October 2021 at 11:06 , Anonymous Anonymous said...

I used the hairdryer method works brilliantly, dismantling and putting back together is straight forward. Not sure how long it’ll last but I’ll be sure to try this tip again. Thanks

 
At 15 October 2021 at 03:46 , Anonymous Anonymous said...

This definitely works. Just followed the instructions and display now fixed!

 

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