iFixit - Answers With Device "Smart Thermostats"

Smart Thermostats: Sensi ST55 thermostat temperature sensor inaccurate/broken

Thu, 05 Feb 2026 09:54:11 -0700

okay this is a longshot. but in the Interest of making things better. i figured i might as well ask. what am i out?

i have a 10 yr old 'smart' thermostat. with a life expectancy of 10 yrs... well almost to the day... it just stopped reading temperature accurately or at all? it was displaying 69° - 72° even when i took ot outside in 10° weather...

i have minimal skill, i have done some soldering in the past. reattached USB micro ports and other fiddly things. but this might be beyond my ability...

i was hoping to offer my dead thermostat for the cause... if someone else is willing to reverse engineer it.

otherwise I have pictures of the back of the motherboard and am willing to take it apart more. to at least identify the temperature sensor or w/e failed. because it seems like it was made to fail.. and we can't have that.

any suggestions or do you need more info from me?

thanks!

I think I might have it, I was on the YouTube just now and watching an off the wall vid recommended by my feed... and something crazy happened at the 11 minute mark...

https://youtu.be/-wEKOhVZ0NM?t=660

there it is is! that's what they look like! and and they are apparently only like $3.00 USD.

and I've found an eerily similar item on the mobo for the thermostat. (circled in red -- in picture below)
[ also note the arrow pointing out venting in the case, as I believe that is there to help facilitate an accurate reading of temp/humidity.]

I do happen to have another image that I took of the PCB, its not great either, but a little better. (I used flash)
with it we can decipher that what I assume to be the temp sensor says: "ANDU"

not sure if that's helpful..

either way here's this image, until I can get home and take some better ones.

so many pictures :D

⟐ Commented February 05, 2026 at 9:54 MST

Tado Smart Radiator Thermostat v3 Plus: Where can I get a new black plastic actuator?

Sat, 27 Dec 2025 11:45:56 -0700

I have a Tado radiator thermostat that has somehow lost the black plastic piece that actually pushes the pin that opens the valve. The device is completely useless without this. Where can I get a new one? I could potentially 3D print one if I could borrow one of these to make a 3D model, or if someone has already done this.

Thank you - Rowan

Lennox iComfort 10F81 Thermostat: Replacement capacitor for Lennox icomfort 10f81 Thermostat

Tue, 24 Jun 2025 05:19:33 -0700

I am trying to figure out the replacement Capacitors for the 10f81 thermostat. There was guide created for this but the Capacitors shown don't match what I have in my thermostat. Here is the link to the guide...Lennox iComfort 10F81 Thermostat Blank Screen Fix. I am attaching pictures of the Capacitors in my thermostat. The Capacitors in question are the "220 HHB. JD4" and the "E 4DB 47 10V".

Somehow I sent the same image. Here is the second image.

⟐ Commented June 24, 2025 at 5:19 MST

Nest Learning Thermostat 2nd Generation: Where can I purchase parts for the nest 2nd generation thermostat?

Wed, 07 May 2025 12:28:41 -0700

Does anyone know where can I get the base motherboard for a Nest 2nd generation?

⟐ Commented May 07, 2025 at 12:28 MST

Nest Learning Thermostat 2nd Generation: nest won't connect to the heatlink

Sat, 16 Nov 2024 07:05:27 -0700

Hi Folks, my nest wouldn’t connect to the heatlink. I’d been on to nest support and they said the system needs to be replaced. Apart from checking version numbers there was no “nest magic” suggested by the support rep, over and above what I’d already tried.

⟐ Commented November 16, 2024 at 7:05 MST

Lennox iComfort 10F81 Thermostat: Lennox iComfort 10F81 resistive touch screen replacement

Mon, 04 Nov 2024 17:02:31 -0700

Hello, does anyone know where to get a replacement resistive touch screen for the 10F81? My thermostat was dropped and the screen broke but the stat still functions. Look forward to a response!

⟐ Answered November 04, 2024 at 17:02 MST

Nest Learning Thermostat 2nd Generation: Nest Gen 2 Battery won't change low lin

Mon, 15 Apr 2024 16:22:43 -0700

I bought a second hand Nest Thermostat and the battery will not charge. The info has a low lin reading of only 8. I know the unit is defective because I bought a brand new one and wired it the same and it works great with a lin reading of 200. Is the defective unit in need of a new battery? Or is it possible there is something wrong with the base?

Thanks!

⟐ Commented April 15, 2024 at 16:22 MST

Nest Learning Thermostat 3rd Generation: Will Nest 2nd generation battery fit in a Nest 3rd generation

Sun, 11 Feb 2024 02:19:35 -0700

Hi,

Will a 2nd generation nest battery fit into a nest 3rd generation thermostat. Ordered the wrong one by mistake.

Thank You,

Jim

⟐ Answered February 11, 2024 at 2:19 MST

Nest Learning Thermostat 2nd Generation: What if my Wi-Fi network goes offline?

Sat, 25 Nov 2023 15:22:29 -0700

If my Wi-Fi network goes offline, will the thermostat still operate as programmed?

⟐ Answered November 25, 2023 at 15:22 MST

Nest Learning Thermostat 2nd Generation: Why does it keep turning on and off? Red light is blinking

Thu, 17 Aug 2023 00:15:27 -0700

Why does the red light keep blinking?

Nest Learning Thermostat 3rd Generation: How to drain battery

Sat, 25 Mar 2023 13:07:33 -0700

The iFixit instructions with the replacement battery says to charge, drain, and charge. Does anyone know how to drain the battery in a consistent way and how long does it take to do so. Obviously, reconnecting the thermostat back to the base won’t work since it can charge from the base.

⟐ Commented March 25, 2023 at 13:07 MST

Nest Learning Thermostat 2nd Generation: Source for replacement battery for the Nest Thermostat v2.0

Wed, 18 May 2022 00:54:23 -0700

Battery as detailed in this iFixit teardown.

Teardown URL

Picture of battery

⟐ Commented May 18, 2022 at 0:54 MST

Ecobee3 lite: Just installed blowing hot air when set to cool

Mon, 09 May 2022 19:51:31 -0700

(old Honeywell wiring)

I just installed a new ecobee3 lite thermostat and I am getting hot air when the thermostat is set to cool. What do I need to change?

(new ecobee3 wiring)

⟐ Commented May 09, 2022 at 19:51 MST

Nest Learning Thermostat 2nd Generation: Where can I purchase Wire Base For nest 2nd generation thermostat?

Fri, 22 Apr 2022 04:43:51 -0700

Where can I purchase Wire Base For nest 2nd generation thermostat?

⟐ Answered April 22, 2022 at 4:43 MST

Nest Learning Thermostat 3rd Generation: Where to find Base Plate?

Mon, 07 Mar 2022 14:07:10 -0700

Does anyone know where I can get just the base plate for the Nest Learning 3rd Generation T-stat?

⟐ Answered March 07, 2022 at 14:07 MST

Nest Learning Thermostat 3rd Generation: Thermostat not calling for heat.

Sat, 29 Jan 2022 22:21:41 -0700

So I decided to buy a used 3rd gen thermostat. I got everything installed. I made sure I hooked everything up correctly as well… When the thermostat is set to heat though it seems like the thermostat doesn’t actually call for heat when in Gas and Forced air modes. I did change the heat source mode to electric and it did turn the blower on ( we have gas so still no heat was made) I also spent time on a support chat with nest for almost an hour trying to troubleshoot with them. Going through resets, updates, double and triple checking wiring to no avail. I’m about to tear the thing apart to see if maybe there is just a loose connection somewhere??

If anyone has any ideas, please feel free to let me know!

⟐ Answer edited January 29, 2022 at 22:21 MST

Tado Smart Radiator Thermostat v3 Plus: Where can I get a Tado radiator bracket?

Wed, 15 Sep 2021 00:55:12 -0700

I bought three Tado radiator thermostats second hand, but one of them was missing the radiator bracket so it cannot be attached to any radiator. Where can I find such brackets?

Nest Learning Thermostat 2nd Generation: Why is the new battery not powering the device?

Tue, 04 May 2021 06:06:15 -0700

I received my new battery for my nest 2nd gen thermostat from I fix it. After I installed it, I charged it with a USB charger. After several hours of charging, the Nest device won’t turn on. When I plug it into the wall, I get a red blinking light at the top. I know I’m installing the battery correctly because, I was able to install the old one and get it to work. Is there a problem with the device or the battery? Thanks!

⟐ Answered May 04, 2021 at 6:06 MST

Nest Learning Thermostat 2nd Generation: I need to replace the outer ring, where can I find that part?

Fri, 11 Dec 2020 16:45:49 -0700

Kids knocked thermostat off the wall and the ring is dented. Now it won’t stay attached very well. I need to replace the ring. Any help here?

⟐ Answer accepted December 11, 2020 at 16:45 MST

Nest Learning Thermostat 2nd Generation: nest app will not connect to the internet

Fri, 27 Mar 2020 22:26:33 -0700

My nest app will not connect to the internet

⟐ Commented March 27, 2020 at 22:26 MST