Lennox iComfort 10F81 Thermostat Blank Screen Fix

Written By: TwoWarm
  • Comments: 88
Lennox iComfort 10F81 Thermostat Blank Screen Fix

Difficulty

Moderate

Steps

22

Time Required

1 - 3 hours

Introduction

I've repaired many modern consumer electronics items by simply 're-capping' them. The capacitors used here cost $15 in total including some extras and shipping. There seem to be a lot of people having failures of these units just after five years (the warranty term). Replacing this unit with an Ecobee or Nest is possible but may require new thermostat wiring among your various HVAC units for the extra wires needed.

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    • You're here because your early-model iComfort screen is blank! The newer Lennox S30 thermostat is the factory replacement for this iComfort, but it cost $1000-$1500 installed (!), so I decided to have a go at a fix.

    • The failure symptoms for my unit included the screen going blank for increasing periods of time over a few weeks before going blank permanently. I could always still control the iComfort via the Lennox iComfort app.

    • Others have reported an all-white screen, lines or odd colors, and since failing capacitors are a common cause of malfunctioning electronics you may have luck with this fix with those types of issues.

    I am looking at this and have the white screen. Can anyone tell me if I need to go down the road for screen replacement or will the capacitors fix it? Thanks

    DanP -

    I think a white screen may be the display panel; others have run into that. In my case the LED backlight driver circuit on the PCB probably failed making a blank screen.

    TwoWarm -

    Just to clarify, do you think the capacitors can fix the white screen or is it the screen replacement, or is it both?

    DanP -

    Did you get yours fixed Dan? If so, did the cap replacement do it? Thanks!

    Skas -

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    • A physically damaged or badly burned-in screen will require a new display panel, around $80 on eBay. I further disassembled my iComfort to get the screen part number. You don't need to do this for just the capacitor repair.

    To get to the screen, the tiny torx (?) screws holding the PCB must be removed and the screen's two ribbon cables disconnected by pulling out the plastic lock tabs on the cable connectors. I ended up just using a flat screwdriver which fit the screws nicely; the screws are self-threaded into plastic and were not too tight. If you have stripes or an all-white screen, those might be screen issues vs. the PCB, but I am not at all certain of that. This screen was around $80 on eBay, in mid 2022.

    I believe there is a small screen power supply (~9V) on the PCB, located at the smallest electrolytic capacitor, that was my issue. There is a small TI TPS61080 power IC and some associated passive components. It supplies only the screen backlight LEDs, and does not power any of the screen electronics as far as I can tell.

    TwoWarm -

    I have the same issue you describe, white screen, some stripes. I replaced the 2 larger capacitors and that didn't do it. I didn't replace the small one, the small one I didn't replace has the number E69n4710v on it and as I reread what you wrote I see that small one is the culprit. Is the E69n 10v cap I just wrote above the small one you're talking about on the PCB board? Do you know where I can get a new one of those? Thanks very much in advance, trying to fix this for my mother on law...

    Skas -

    TPS6108x High-Voltage DC-DC Boost Converter With 0.5-A,1.3-A Integrated Switch

    It appears that the PCB uses one of the reference designs, and supplies a variable pulse width to adjust the screen brightness.

    TwoWarm -

    LCD screen datasheet (similar version)

    The backlight is shown on pg 9.

    TwoWarm -

    • Lightly press anywhere on the screen to make sure the screen saver is not active. Is the top of the thermostat slightly warm? Is your heating/cooling still working normally? If so, power is likely present and the iComfort itself may still be operating correctly.

    • Hopefully, you or your installer have previously registered your iComfort with Lennox, and you have the iComfort app installed on your cell phone. If so, can you still access and control your iComfort via your cell phone? Good chance of a fix if so. If not, the screen used to work and now it doesn't, so little to lose...

    • First, turn off the circuit breaker to the indoor unit (also called ventilator, heater, fan). Grasp the iComfort and tilt it downwards to unsnap it from the wall mount. Place the iComfort face-down on a smooth surface.

    I'm not sure I understand what you mean by ventilator heater fan should I just turn off the breaker for the unit

    Mary Wittig -

    Disregard the previous statement I did find the switch on the furnace to shut down the fan

    Mary Wittig -

    My system today has the white screen with the colored stripes now so I want to shut it off so I don't destroy my screen

    Mary Wittig -

    I suspect the LCD display itself may be bad; you can find them on eBay for ~$80 (Feb 2023)

    TwoWarm -

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    • Using the guitar pick or small flat screwdriver, gently pry the bezel rim away from the back plate to free the locking tabs. Take note of the small sensor glued into one corner and start your prying opposite to it. There are 10 tabs, but after you get the first 3 or 4 free the rest are easier. Just don't pry beyond what is needed to clear the tabs!

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    • There is nothing attached to the back plate so just set it aside. The capacitors may have some glue stuck to their bases. Just pick this off; it was used to hold them in place during assembly and need not be replaced.

    Are the ones boxed in yellow the capacitors in question

    Mary Wittig -

    Yes. A total of four.

    TwoWarm -

    Your design layout is different than mine and I have a capacitor that you didn't identify that's got a lot of oil that escaped LOL

    Mary Wittig -

    The one that I have oozing is the big one on the left bottom it's a 5.5 volt 1.5 ft from what I can read of it where would I get that and these Replacements that you put installing are these the same manufacturers that were in the original installation or are these better

    Mary Wittig -

    I was going to send a picture but it won't allow me to do so on this site but my design only has two of those 220 capacitors and then the one that leaked oil and then that little is it a 47 one point microfarad e62 way none of those look like there is anything wrong with them did yours look like they were leaking like I said the only one that seems to be leaking on mine is that big one on the left

    Mary Wittig -

    None of my capacitors looked bad. What happens is their internal electrostatic resistance (ESR) increases as they age. There is some old glue or epoxy that was used to hold down the caps, but it was solid and dry; if you have a liquid or soft goo then a cap definitely failed.

    I later changed the large super-cap, but it didn't help anything. It just preserves the t-stat settings during a power outage. You can substitute other makes, just make sure the package size matches so the leads fit into the PCB.

    Eaton 1.5F Supercapacitor

    TwoWarm -

    I hate to keep bugging you but when I go to the links they're both identifying for the on my board c283 and C270 none of the links are identifying c258 which is the e62a47 10 volt

    Mary Wittig -

    I went to your suggested site for the Eaton and they're out of stock I did however find a Panasonic that had the same values but it was priced better but if you don't buy more than an allocated amount they charge 10 in shipping

    Mary Wittig -

    Considering that my screen never went black however with your current statements of failures I probably get those caps but there again my design is one cap short than what you had posted

    Mary Wittig -

    I fixed my 47uF capacitor link at top, and it is now apparent to me that there are several major revs of this PCB. See my comment at bottom for a link to the Panasonic 'HB' series capacitor data sheet, which lets you construct a part number for your caps based on their package markings.

    For the super-cap the most important thing is the package size/style (besides voltage rating); any value from 1-2 F will probably work fine. These caps seem to suffer more from supply chain issues than most, so may be hard to locate. Good luck!

    TwoWarm -

    EEE-FN1A470UR can be purchased in stock at www.newark.com

    EEE-FT1H221GP can be purchased in stock at www.mouser.com

    Jay Cox -

    I had an issue with the 1.5muf 5.5v super capacitor and unfortunately while replacing it, messed up the polarities. Smoked a couple of components C88 and U6 next to the capacitor. In the absence of a circuit diagram, have no way of identifying these component specs :(

    Danish Jamhari -

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    • Dab some flux onto each of the capacitor terminals; this helps the solder melt and flushes away any oxides. Apply your soldering iron to the capacitor solder tabs; gently pull up on that side as the solder melts and the capacitor should lift up. Repeat for the other side and remove the capacitor.

    Click on the 'for sale from another site' link in the 'what you need' box at top, to see the capacitor vendor's webpages.

    TwoWarm -

    How did you remove the two small screws to get the PCB off the screen I've tried my Allen sets and I don't have anything small enough to fit and I tried some Torx but my Torx are also too big

    Mary Wittig -

    You can go to harbor freight and it is a Torx T5.

    Search their site for Torx T5 and there are a few options.

    PITTSBURGH PRO

    TORX Tamper Proof Hex Key Set, 7 Piece

    Alex F -

    A small flat screwdriver fit and worked for me.

    TwoWarm -

    I used needle nose pliers to remove those two tiny screws. But then it seems all the soldering work can be done from the top side, without removing the two screws.

    Robert Inouye -

    • If you just can't get the capacitor free, gently rocking and twisting it will eventually break the leads, and you can then easily de-solder the ends still stuck to the circuit board. Proceed at your own risk!

    This is what happened to me. I had to do some civil war surgery with jumper wires, but got it back together.

    pdet -

    • Remove any pieces of leads, and clean up the circuit board solder pads by just running your soldering iron over them. Apply some flux to the pads, and position the new capacitor.

    Where were you able to get the capacitors

    Mary Wittig -

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    • PLEASE observe the proper polarities or else damage will occur; look at the pictures; the three large caps all face the same way; the single small cap faces opposite. The white outlines on the circuit board nicely match the shapes of the capacitors' black plastic bases - note that one side has beveled corners.

    I know this is an older thread but obviously I’m at that point in the life of my thermostat. However, the numbers on the top of my capacitors are different from the ones in your pictures. How do I find the correct capacitors for my circuit board? So I have 3 on mine. 2 of which are the same. The 2 larger ones read:

    220

    HHB.

    K78

    And the smaller one reads:

    E372

    47

    10V

    Any help would be awesome. Thanks

    vinnylastella -

    There are multiple part numbers that will be compatible. There are some links in this writeup for parts at Mouser. I used DigiKey, and here are the ones I bought:
    https://www.digikey.com/en/products/deta...

    https://www.digikey.com/en/products/deta...

    Hope this helps.

    pdet -

    • C283 is a bit of a tight fit on one side; you can move the new capacitor slightly away from the adjacent component to give yourself more soldering room, as long as you can still get solder onto the circuit board pads.

    • Apply your soldering iron and some solder to each capacitor tab, heating for long enough that the flux boils and solder flows onto and between the circuit board pad and capacitor lead. The joint should be shiny. Do the other side, and give the capacitor a gentle wiggle to insure the solder joints are good.

    • Repeat for the remaining capacitors and you're done! They will have a tiny bit of play when you nudge them. Optionally, you can remove any excess flux using alcohol wipes or isopropyl alcohol and Q-tips. Look for any stray balls or pieces of solder and remove those.

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    • Optional: I used an old doorbell transformer to supply 24VAC to the 'R' and 'C' terminals of the iComfort; it works fine without being connected to the wall plate. I tested it in this state for a week before re-installing it.

    While you were testing your unit you were able to function your system by your phone or you just didn't have anything running for your system

    Mary Wittig -

    When the thermostat was blank before I fixed it, the Lennox app could still control the HVAC system. Just the display was dead. However, I have seen on the internet that this thermostat can have other failures, such as its wifi module.

    TwoWarm -

    After working fine for quite awhile, a nearby lightning hit or electrical surge during a storm seems to have damaged the unit (no display or wifi control). The surge also damaged some other sensitive electronics so I'm fairly confident it would still be working otherwise. Oh well, time for an Ecobee, which unfortunately requires running additional thermostat wiring since it uses the standard non-proprietary (non-communicating) thermostat interface. I may try additional troubleshooting on the iComfort at some future point.

    TwoWarm -

    Good to know

    Mary Wittig -

    When I apply 24VAC, thermostat boots to System Alert error 12: incomplete system. There is an X in the right top corner that when touched will reboot it to the same state. How do I get it to home screen?

    mi wo -

    • Replace the back cover plate by carefully snapping the tabs back into place. Hook the bottom of the iComfort onto the small tabs on the wall plate, and swing the top of the iComfort back into the wall plate until it snaps into place. Turn the interior unit circuit breaker back on.

    • It may take a minute or two for the iComfort screen to illuminate even if the repair was successful. I would leave it on overnight before giving up.

    • If successful, the iComfort screen will be on and may show some error warnings. 'X' out of those and the screen should revert to its normal appearance showing temperature, etc. Now, IMPORTANT, SET THE DATE & TIME by pressing on the clock display at lower left. Getting within a few minutes is OK.

    • The iComfort WILL NOT re-establish its WiFi link to the Lennox iComfort server unless the time/date is pretty close. This is not mentioned in the user manual! This step is required if you use the iComfort app, and/or you want your local weather to appear on the display.

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    • I pulled some of the pads off while removing the caps, and had to add jumpers, and use the unpopulated cap slot (I checked for proper connectivity)

    How do you find where the jumper cable is connected to? I happened to remove a pad on the left 220muf capacitor (mine is in the slot below your corner capacitor) and could not identify where the jumper can be connected on the pcb.

    Danish Jamhari -

    @danishjamhari -- you can verify with an ohmmeter, you just have to scrape off the soldermask to expose the remaining trace. If you are referring to the capacitor in the top left hand corner (I should have noted the reference designator), you can put the replacement capacitor in the top slot where I installed mine. They are connected in parallel, so either slot should work.

    pdet -

    Thank you for your reply.

    Danish Jamhari -

Conclusion

I recommend going through any custom iComfort settings to verify they survived (mine did, for 8 months), and I also turned down the screen brightness to the lowest setting of 20%.

Author

TwoWarm

Member since: 09/12/22

526 Reputation

47 comments

I have an iComfort 10F81 thermostat that still functions, but has the white screen of death, so I cannot change any of the settings. It came with the home (purchased not long ago) so I do not have an app connected to allow me to make any changes. I was really happy to find this webpage and order the parts. I've had to do a fix like this before on a BMW 3-series HVAC control unit and saved myself $600. Unfortunately when I cracked my unit open and was getting ready to do the repair, I found the PC Board did not match what was shown (mine only had two large caps and a small cap) and the capacitors listed here were not the same as the ones on my unit. Sadly I will have to order the correct capacitors and hope I can find them in stock. For reference, the Part# on my unit is 103445-04. If you plan to attempt this fix, I recommend opening your unit before ordering parts to verify the capacitors you need.

John Buck -

If you're able to reply, I'm not quite sure how to find the right capacitors for my unit. The larger ones read "220 HHB K27" (they are physically about 20% larger than the ones I ordered according to your part numbers); The smaller cap reads "E 723 47 1 0V" or maybe "1 QV" or maybe "10V"

Also, FYI, both of the links in the "What you need" section point to the same capacitor page.

John Buck -

@John Buck - I have the exact some caps in mine; Did you figure it out? I am unable to find anything like these to replace them with!

Craig Smith -

@craigsmith65430 - Using the data sheet that @twowarm posted in reply to my post, I was able to determine that the capacitors (caps) suggested on this site were indeed fungible with those on my unit's PCB. They were different sized, but the voltage codes and capacitance were the same. What's interesting is that my PCB DOES have the pad for the 3rd cap, but doesn't look like one was ever installed. I think I snagged the last caps that were in stock in the above links, so you might need to find a way to source other comparable caps. Again, this link posted by @twowarm was very helpful and could probably serve as a starting point to find caps from another source. I'm not 100% sure, but I don't see why you couldn't use caps w/ the same specs from another MFR

I'm running into issues currently due to my lack of soldering skills, but if I get everything swapped out, I'll probably post a youtube video on the fix. @twowarm are you ok with me posting a vid and giving you a shout out, if I'm successful? I will include a link to this page as well.

John Buck -

Sadly this fix failed to work for me. Difficult to say if it was due to something else being wrong, or if it was simply my terrible soldering job! I had a terrible time probably because my soldering iron was not getting hot enough. One of the pads came off of the circuit board, so that was fun. I got all three caps soldered back on, but the white screen persisted. Looks like rewiring the HVAC for a standard thermostat is my next stop :(

John Buck -

Were you able to get it working with the 2 larger cap replacement? Thanks in advance!

Skas -

John, I believe the capacitors are still Panasonic 'HB' series; their overall data sheet is at:

https://api.pim.na.industrial.panasonic....

You can generate the part number from this then go looking for vendors.

Thanks for catching the link error, I updated it!

TwoWarm -

Hi…my thermostat is not blank. It is white with various shades of grey. I am not able to connect to it through the app but the thermostat was removed, as recommended by my HVAC technician, for days and the time is likely off by a lot. Is this likely just a screen replacement ?

Bill R -

White with shades of gray means circuit board is bad, not the screen issue and not the capacitor, you need to find a replacement unit or upgrade to S30. https://youtu.be/gDeXEU7W5BU?si=NmP9K4Mq...

Li F -

Anyone know what constitutes good capacitors. On the 220 microfarad, I am getting 203 and 207 (I have the design with just two). Could this be my problem? On the 47 microfarad, I'm getting 53, so I'm assuming this capacitor is fine. I can find the 47 microfarad in stock but the 220 seems to be out of stock and not expected until August.

Bill Rector -

Electrolytic caps often have a +/-20% tolerance range (or even wider). The usual failure mode is a high ESR (electrostatic resistance) as an electrolytic capacitor dries out, and it is difficult to directly measure since it is usually down in the milliohms. High ESR limits the capacitor's response to switching transients, and a failing-ESR capacitor will often show a normal capacitance. I would search around different vendors vs. re-using any old caps you've already removed.

TwoWarm -

Hi:

I am not very good at repairing things myself. I am in a similar predicament. Have a Lennox 10F81 with a blank white screen, Would you be able to fix it for a fee. Please let me know . You can email me at oosman_abdulla@hotmail.com.

Thanks

Oosman Abdulla -

The white screen may be a display panel issue; these thermostats seem to last 5-8 years then start having various issues. Sorry, I can't do commercial repairs.

TwoWarm -

Are there places or companies who can fix the icomfort screen problem?

Anil Sachdev -

If anybody here posts a fix on another site, please just cite this webpage. I'm not aware of anyplace that repairs these units. I'm not sure what prompted Lennox to switch to a cumbersome hub-type unit for use with multiple thermostats when >90% of houses have just one. Lennox has a decently-priced smart thermostat but inexplicably did not include their own proprietary iComfort interface. Lesson learned, on my next HVAC system I'll spec standard thermostat wiring.

TwoWarm -

I was wondering if anybody has had any other issues with the 10F81 besides the screen? Mine looses all the program settings when power is lost. In addition it is constantly loosing the wifi connection and defaulting to the default cooling (loose all programing). I constantly have to reconnect to the wifi (add password) and re-enter my programs. Any insight would be appreciated. Thanks,

Ken -

The large disk-shaped 1.5F capacitor is probably bad - this provides a keep-alive power source for the t-stat's volatile memory.

TwoWarm -

Was anyone else successful with this capacitor fix?

Warrior fix -

Replaced caps still no screen, the unit working without screen , I can still control the temp with the app.

Joseph Chalhoub -

The main circuit board had some other malfunction, your next best option is to buy another unit with a working screen, or upgrade to S30.

Li F -

Thanks for this guide. My 10F81 screen is fine but the thermostat continuously changes the time (goes to different timezone?) and therefore connection to server. I can reset the time and then reconnects to server but soon faults back to wrong time. With wrong time, schedules don't work. I read elsewhere that this date/time loss can also be fixed by replacing capacitors... does this make sense to you?

Gizmo -

There is a build-in re-chargeable battery on the circuit board that stores time info, the main circuit board battery is probably bad and needs to be replaced. Most likely your thermostat loses power and when that happens, time info gets reset, and it won't connect to WiFi if time is not set correctly.

Li F -

The large disk capacitor saves the time/date for a little while (hours?), the other caps are just power supply support, I believe. You might have glitchy AC power (24VAC) to the t-stat, which could cause reset issues. Any flickering house lights, etc? I would examine & change the disk cap only, for a start. I would also gently pull out and re-seat the flash memory card (inside the black housing) a couple of times; it may be used to store certain settings as well.

TwoWarm -

Hi there, my 10F81 also stopped working. Where can I get those exact capacitors or equivalent. Thank you.

Paul -

If you have a white screen instead of blank, it's definitely the capacitor, I replaced my blank white screen with a new LCD screen from another 10F81, same issue, so you just need to get proper sized capacitor (Oldest version of the 10F81 uses 3 caps, while newer firmware/hardware uses only 2 Panasonic EEEHBH221UAP 220uF 50VDC capacitors instead of 3) You can get them here: https://www.mouser.com/ProductDetail/667.... The small capacitor is Chemi-Con APXE100ARA470ME61G 47uF 10V https://www.mouser.com/ProductDetail/661... Hope it helps. I'm gonna give my board a try before I toss it out and get the S30 installed.

Li F -

I just made a video on how to replace the LCD screen. https://youtu.be/gDeXEU7W5BU?si=NmP9K4Mq... Also to save yourself time and trouble, if your screen shows a white image, it's also NOT the screen and NOT the capacitor, the main circuit board is a toast, and it's time you find a replacement unit... I replaced all the aluminum caps on my circuit board and it still is broken with white blank image on the screen.

Li F -

Hello, mine has the 2 larger caps but they have the number 220HHB.06 on them. Will the caps in the link you provided for the 2 cap model still work? I cannot find replacements when searching for the 220hhb06. Thanks very much in advance!

Skas -

On this post you said if "you have a white screen instead of blank, it's definitely the capacitor"

And on another you said if your screen shows "a white image" it is "not the capacitor and not the screen, you need a new unit"

Can you please explain the difference between the "white screen" and "white image"? I don't understand what you mean. Mine is a pure blank white screen.

Nicholas Gayliard -

Have an 88w58 screen is black. When Blow hot breath into it the screen lights up for a few seconds, looks normal, fades out, makes a slight high pitch noise, then turns black again. Is this fixable with new capacitors or is it toast? Who wants to start a class action lawsuit about these designed to fail thermostats.?

David -

Thanks VERY much for this info. I tried finding info to fix my sister's Lennox thermostat (10F81) but wasn't able to. Hers had the typical "fade to lines then black" symptom. I ended up replacing her thermostat with a new Lennox S30 thermostat, and of course, integrating the hub as well. A lot of research and work, but it got her system working again.

But luckily, I kept her old thermostat, and ordered the capacitors from Mouser, and replaced them this morning (I used to do electronic repairs in a previous life). A few things I noticed... 1) Her unit only had two of the three "big" capacitors. I suppose that's just because of a production change. 2) When I unsoldered one lead on the first "big" cap, it came off the board - the solder joint under the second lead was obviously cold (might have been the actual problem - who knows?). 3) I suppose it might have been worthwhile to replace the keep alive battery (5.5 volt button cell, soldered in).

Mark in Mesa, AZ -

Thanks for this thread!! When plugging my 10F81 into wall mount and powering up, my screen has full pixels gray background and displays three tiny rings in the center (rings alternate to solid - looks like it is booting up). This lasts for 1-3 seconds then screen goes black every time. I also noticed the big disk capacitor (5.5V/1.5F) has oil/flux around it! Hmmm.

Almo 718 -

I'm in the process of trying to do a cap replacement now on our 10f81 with a white screen. I have the newer model with the 2 larger caps but mine say 220HHB.06. Unfortunately I already bought the smaller ones before I opened it. In the comments above, one person wrote that the smaller replacement works to swap out the big ones (says they're fungible, same wattage). Another person provides a different number for replacement of the big ones. Has anyone with the big ones successfully repaired theirs using this method? Thanks!

Skas -

I just replaced mine with the parts in this guide, no issues. I can share video or pictures if you want. Let me know.

toncast -

Mine is 10F81 also started malfunction. My thermostat is 6 years old. Like 6 months ago it was a power outage in my area. After that my touch screen was black and didn't respond on my finger touching. I detached my thermostat from the base and plugged back. It started to reboot, and screen comes up as usual. It was working for a week and stop working after. I have also 2 big capacitors 220HHB.395 and 1 small E578 47 10V. My circuit board is 103555-02 REV 9. 2011 Lennox Industries Inc. I can still use my app on my cell phone to control my system.

Called today to my system installer and Lennox technical support. No detailed information on repairs and parts. All information confidential. They suggested to replace thermostat on S30 ($1500 just unit).

I am going to buy 2 Panasonic EEEHBH221UAP 220uF 50VDC instead my 220HHB.395 and the small capacitor is Chemi-Con APXE100ARA470ME61G 47uF 10V to replace my old E578 47 10V as suggested Li F. I will keep you posted on my outcome.

Thanks to everybody for this discussio

Alexander Predtechensky -

How'd it go Alexander?

Skas -

Alexander,

Curious if this worked for you? I also have a white screen. Unit is still running my heat pump, thankfully. I just can't see anything on the screen or change any settings. I was able to control it with my phone for several weeks, but now I lost that connection. Do the capacitors fix the white screen issue also?

Nick Lam -

If I purchase the newer S-30 model, will it just plug in where the old one was? or will it take a service technician?

David Demers -

You will need to call in a technician most likely

toncast -

Does anyone on this thread know if the Google nest or something similar will work on the Lennox system. If so is there a link or anything saying what product works best and how to wire the unit

Any help would be great

Thank you in advance!!

Duckett80 -

No, these are proprietary communicating systems. Standard thermostats will not work without changing out the control board at the HVAC unit, and disabling the "communicating" feature which improves the efficiency.

pdet -

Please refer to this post on how to change to conventional wiring (non-communication wiring).

https://community.smartthings.com/t/lenn...

Mian Qin -

WE FIXED IT! We had a blank screen. We went to our power source and turned off the furnace at the breaker box. Waited 30 seconds. Flipped it back on. Wah-la, the thermostat reset. (There was also an on/off switch on the furnace which I did the same thing with, not sure which one worked.

slitch -

I have the thermostat that only has the 2 big capacitors and one small one. I replaced the capacitors and when I powered it up, it started out working ok for a few seconds, then slowly fladed to white. I thought maybe something was wrong with the screen, so I ordered a new screen and replaced that. When I powered it up, same thing, it worked at first for a few seconds, then faded to white. I opened it back up tonight and checked capacitors incase I had a bad one, they all tested good. I then pulled one terminal on the super capacitor and tested that. It tests bad. Could that be causing my problem, or does that have nothing to do with the screen? If you have any insight, please help.

Joshua Westlund -

My issue was the screen going dark due to a bad 9.6V power supply; I suspect that in your case that there is a screen driver issue instead. The only 'easy' attempt to fix this is to reheat the appropriate ball-grid surface-mount IC to re-flow the 10s-100s of tiny solder connections beneath it. This is a common failure mode in consumer electronics, probably just behind bad caps. A local electronics shop can often do this type of repair; re-flowing all of the ICs (and other components) at once is actually easiest since they can use an oven. It does require some special equipment called a 'hot bench'. I'm beginning to think that the same issue is causing my problem as I get odd output signals from the small power IC. Since the ICs themselves rarely just fail, the soldering is usually the weak link. I fought with this in military applications for years; surface-mount offers some electrical benefit but mostly it's cheapest. No guarantees this will work but I may try it on my unit.

TwoWarm -

It's interesting to see that hobbyists often use a toaster oven to do this, but I'd find a shop that has the correct equipment.

TwoWarm -

Thanks for the insight I replaced the super capacitor (before reading this) and that didn't help either. I think I'm going to just get a honeywell T10 and pull a new wire. Then flip some dip switches and make the furnace a one or 2 stage, with 2 stage AC and a humidifier atleast with a Legacy thermostat, I can test and replace parts easier. Thanks again.

Joshua Westlund -

I found one post that mentioned they disabled the wifi and the problem of the 10F81 resetting itself every few minutes and losing the date/time went away. I tried this and it did indeed stop resetting. I am waiting for the super cap to arrive and will replace it and see if that cures the whole problem and I can enable the wifi again. There is a YouTube video that has a guy who refurbishes the 10F81 and sells them on Amazon, but he appears to be out of stock or maybe out of the business now? He mentions in the video there is an Allied air thermostat that is made by Lennox and it is a direct plug in replacement - just does not have the wifi option. He did not indicate the model number, and I have not found this replacement option yet. Here is the video:

Blank Lennox iComfort 10F81? Here are 3 FAST solutions! (youtube.com)

Wilbert Lee Pogue Jr -