I have a two zone scw geothermal system using a ClimateMaster 27 TTS system. Things have worked fine. After reading this forum and the amazing advice from so many knowledgeable folks here, I decided to check on some of the settings that were on my thermostat. Unfortunately, I don't know if it was a coincidence, but this afternoon, one of my Honeywell T-stats (both are the same model Visionpro TH8321) seems to be acting up. The backlight on the screen does not go off as it was set up to do, and some of the buttons do not work or take very long to respond. For example, the schedule button does not work, the system button sometimes responds sometimes not. I removed the front, removed the batteries and put them back to see if that would make a difference. Does not help! Since the schedule button or system button don't work, it is not possible for me to even go to any setup screen. Is there anyway for me to reset this t-stat and get it working again? Any ideas? Thanks! Sam

I'm not an expert. The only thing I can think of is to do what you already did, but leave the battery out for a longer period of time (I can't define what a long time is.) Some electronic devices can hold enough power (short term) to remember settings when the battery is removed for an insufficient amount of time to reset the devise. Not sure if thermostats work this way. The customer support number for Honeywell is 800-468-1502. Good luck.

I believe there is a "reset to factory defaults" choice somewhere in it. That's worth a go. It's possible a connector between the screen and the PCB is loose.

You may need a new stat.

The Honeywell TH8321 thermostat is back to normal operations again! Not that I have a very good theory for why it came back to life this time!


It was doing some really bizarre stuff - like the backlight not going off as it should have, no response to the SCHED key or DONE key. When I managed, one or two occasions but not always, to see if I could change settings to reset the thermostat by getting the SYSTEM key to respond, it would cycle through the various options but not let me choose anything. And if I managed to get the CLOCK key to respond, the clock would automatically wind down and not let me set any time.


I even removed the batteries several times, sometimes for about an hour and see if that solved it. No dice.

In a final attempt, I removed the batteries, blew around the PCB and in the gaps in the assembly, and wiped the contacts (even though they looked fine and shiny), replaced the batteries and that seemed to do the trick.

I have no idea why it worked. Maybe there was some static? Maybe some dust? But it sure seems to have worked.


Thanks for the help from the amazing folks in this forum.

Sam

Part of the touch screen may have been registering as if it was being pushed, even though it was not. If it happens again, disconnect it and try lightly pressing your finger on the screen and gently rub your finger back and forth making sure you don't miss any areas of the screen. Worth a shot if it acts up again. For now, don't fix it if it ain't broke. You could always start checking into prices (your dealer and online) so you will be prepared the next time it goes out (hopefully never).

I know this is an old thread but I found it on Google and there wasn't a very good answer in the thread.  I had this same problem and was tearing my hair out, wondering if my 6-month old Honeywell TH8321U (similar to the TH8321U) was now a brick.  Anyway I finally figured out the hard reset.

Pulling out the AAA batteries isn't going to reset this thermostat, no matter how long you leave them out, because there is a little button cell battery mounted on the circuit board which prevents a reset! 

To get at this battery, remove the front faceplate.  The faceplate is removed exactly the same way that the thermostat is removed from the wall plate.  Press the vent tabs in and pull firmly.  It takes more force than pulling the thermostat off the wall.

Make sure the AAA batteries are removed.  Under the faceplate, you should see the LCD in all it's glory.  It is secured by 2 "Tab arms".  Push the tab-arms to the side, and pull the LCD and circuit board off of the back plastic backing piece.  It should come apart very easilly.  Now the Coin-cell backup battery is exposed.  Take it out for about 10 seconds, put it all back together, and everything should be working again.  You will need to reprogram everything....

This worked for me. I had a similar problem in the spring and I must have pulled the battery at that time also, worked fine for 6 mo. When I put the battery back in, everything was working except for the done button – the most important button on the unit. After wiggling the display around a bit, the done button also worked. I'm guessing that the display ribbon cable must have been slightly out of alignment in the clip. I also replaced the button battery while I was at it even though it was showing 3v on the meter - this was my electrical (just one decimal) not electronic meter so it could have been a bit low and rounding up. I'll likely replace it with a NEST thermostat after the first of the year – initial batch all sold out. Thanks for the help.

The button cell back-up battery was the answer for us. Took the thermostate apart, took out the obvious batteries, and then opened it up further, and removed the button cell for 10 seconds. Took a bit of reprograming (as you would a new unit), but worked like a charm! Its so logical... Great comments, and Thank you so much!