Ok, I've searched the web for an answer without any luck so I'm going to ask here. I have a carrier unit (not sure what size) that was installed several years ago along with a Honeywell thermostat. Everything worked great but about a year ago, the thermostat screen would go blank randomly. I thought it was the batteries but the unit didn't have batteries. So I thought the thermostat was bad, so I replaced it with an upgraded Honeywell smart thermostat.

Everything thing seemed good but after a couple of weeks, the blank screen started happening again. This time I noticed it only happened when I would manually adjust the temp through the Honeywell app (doesn't make sense). So I quit adjusting through the app and only did this at the thermostat. I don't adjust all the time since it is set up to do that automatically but sometimes we want it just a bit warmer or cooler, a degree or two.

Now it is happening while adjusting the temp on the thermostat. And it always happens after the furnace or ac has kicked on causing it to just run and not shut off. I have to pull the thermostat off the wall and replace it for it to reset (touchscreen). I've had a hvac company out to check it and they said everything looks good and couldn't find a reason for this.

It is so weird that this is happening with two different thermostats. If anyone has any ideas let me know otherwise I'm calling a different hvac company to check it out.

pnut02 said:

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Bad control board (inconsistent source of power) or defective wire from the unit?

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exactly what I was going to say...the common wire (usually red) provides voltage to the thermostat. Need to open up your control board and make sure the wires a good connection (and the wire is still good and not chewed or burnt)

Thanks for the replies. I was thinking it could be the wiring, but that didn't make sense to me since the only time this happens is when I manually adjust the temps. And even then it doesn't happen all the time. I'll get someone out to look at it since this is past my level of knowledge.

We had this exact same problem a few years back and it was the control board. I found an exact match on Amazon and installed myself. They are plug and play. Just be sure to take pictures before you pull anything apart. I think the control board was $200 to $250.

Me too
Friends/sports buddies installed their brand Carrier - at forst A-OK
1980, 1999 but all those troubles in my rear view window with Trane now
and those Carrier installer guys were tops in the biz ... its the brand, so sorry
and I don't ever mean Honeywell, the very best

GigEmAgs08 said:

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We had this exact same problem a few years back and it was the control board. I found an exact match on Amazon and installed myself. They are plug and play. Just be sure to take pictures before you pull anything apart. I think the control board was $200 to $250.

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Thanks for the info. If it's that easy I'll crawl up in the attic this weekend and take a look at the board and see if it's something I want to tackle. Though it's be working fine the last few days.

Quote:

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Me too
Friends/sports buddies installed their brand Carrier - at forst A-OK
1980, 1999 but all those troubles in my rear view window with Trane now
and those Carrier installer guys were tops in the biz ... its the brand, so sorry
and I don't ever mean Honeywell, the very best

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Ok, not sure what all this means.
I currently have a Carrier system installed about 5 years ago. This is the first issue that I've had with it. Does seem the control board would last longer than that, but I guess it's like anything else nowadays. Had a Trane before that and had a lot of issues with it. But maybe that was more the installer than the system itself.

Your AC unit and high-efficiency furnace generate condensate during operation, which usually drains into a sink in your home. If the condensate drain line becomes clogged, the accumulated condensate can trigger a float switch that shuts off the system to prevent overflow. When your system stops unexpectedly, remove the float switch and inspect the line for water, indicating a potential clog.

If the thermostat is momentarily going blank but coming right back on we have found more than once it was due to a short in the low voltage wiring. Many of the times it was bare control wires between the house and the condenser that would under certain circumstance (mainly being wet) would cause an issue. Other times it was bad contactors on the outdoor units.

Another poster mentioned a drains safety switch and that must be considered as well.

However, as a full time HVAC professional, I will say with certainty that Honeywell (now Resideo) is absolute garbage. I will only install a Honeywell product if I am forced to. I ordered 36 T6 and T6 Pro thermostats with our logo on them and within 12-18 months I had replaced 20 of them under warranty. Failures included calling AC on but not the fan, temperature reading five degrees off, heater running with no call for heat (restaurant had gotten to 85 inside before owner yanked it off the wall to get it to shut off), repeated time delay, faulty display etc. I sell and install Emerson thermostats now and I've had a good success rate. In over 100 sold I've had less than five have issues and the oldest one I've got out is about three and a half years old now.
Keep us posted and let us know what you find.

Interesting. I wasn't set on replacing the previous Honeywell (T6 Pro Smart) with another Honeywell (WiFi Smart Color) but wasn't sure what else to go with, other than a Nest, which I wasn't excited about.

I have regular service done (twice a year) and asked the techs a few months ago to check out the issue. They went through and tested everything and couldn't find an issue. The only thing they mentioned was the flame sensor would need to be replaced soon, which they did a month ago during their check.

The problem originally started with the T6, which was only about 3 years old at that time. I just thought the thermostat was bad which is why I replaced it. Everything worked fine, for a bit, and then it started happening again. So that's when I thought it wasn't the thermostat. This is why I generally stay out of trying to fix these sorts of issues. It sounds like it could be a few different things.