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Furnace Short Cycling

mjgribbins
Community Member
 My nest thermostat is making my furnace short cycle (turning off and on every few seconds). I have the c wire installed. I re-installed my old (non-smart) thermostat and the furnace worked fine.
 
I checked the connections at the nest base plate and they are pushed in and the buttons are down. I have the G wire, W wire, R wire, and the C wire connected to the correct ports on the thermostat and at the furnance.
 
My batteries have hovered around 3.0 V, even several hours after the connections were made.
30 REPLIES 30

Kingfor
Community Member

Following.  The same thing is happening for me.  Would like to know if you have resolved the issue.

 

Thanks

fedino82
Community Member

Same here with the Nest telling me that the furnace shuts down every 15 mins and to check filters. The furnace does show an overheating error / limit circuit fault code 33.

I changed the filters and had the furnace checked by a technician: he had the furnace running for 2 hours and never stopped nor give an error code.

I then removed the thermostat and connected red and white wires: the furnace works continuously, never stops and no error code.

Hence, this error is caused by the thermostat.

Mine was turning off and on every few seconds. I called customer service and they said I had to hook up the thermostat and call them back, which I've yet to do. I switched back to the old one figuring that cycling off and on every few seconds can't be good for the furnace.

DDT1345
Community Member

Same issue here. I also can't believe that this is good for my furnace. The relay on the Taco Zone Valve Control board is clicking like crazy...and I have a C-wire installed.

Lizzyf
Community Member

Following. Same and I cannot find an answer

ace008
Community Member

Same issue here.  Eventually in the mornings after a few of these short cycles, I have to flip the breaker to the furnace to work again.  I also did a hard factory reset.  Before the reset, the furnace would not come on at all.

mikep151
Community Member

I have the same issue with short cycling.  Sometimes the furnace kicks on and runs as it should.  Other times it just spools up and then stops over & over again.  Batteries are at 3.6-3.83.   When it short cycles I have to manually turn the temp down below current room temp until the furnace stops cycling, then turn it back up.   Then the furnace will start up.  I do not have a C wire, but it sounds like that's not really the issue.

Hello, This is an old post, but I'm wondering if you found a solution as I am having the same issue.

 

My issue was with the condensation trap on the furnace. Had someone come out and look at it, they did a little cleaning and routine maintenance, issue wasnt the Nest.

Spray
Community Member

Yea my entire home is brand new so that’s not what it is here

carndog
Community Member

I have the same issue.  Using the same nest and system for 4+ years, problem started a few weeks ago.  Swapped out the nest for an old thermostat and the short cycling stopped.  Almost seems like a software update was the root cause. 

Bethzdo
Community Member

My furnace keeps recycling I have even had a new thermostat sent to my and  installed it keeps recycling. I went back to my old thermostat. I wish they had a better customer service program 

Spray
Community Member

I’ve had two replacements now and hvac ppl here 5 times! Still don’t work 

Azúl
Community Member

Same issue. Nest is short cycling, but backup thermostat works fine.

WD40
Community Member

Same issue. Returning the Nest--disappointing and a waste of time--and reinstalled the old thermostat which works fine. 

Kabes
Community Member

Same issue here.. Can't figure it out and its driving me crazy.   On the phone with google and they suggested i replace it with another one as it may be defective.  Returned it and installed another one and same thing.  C wire or no C wire it doesn't make a difference,  Fed up and Reinstalled old thermostat and going to return the headache.  

diyx123
Community Member

Anyone able to figure out their on/off cycline issues? I also had this issue last year.  Turned out it was my water limit guard dog.  I'm having other issues now that could be related to the Nest / Taco board.  Would be interested in knowing what fixed your cycling issues.  Thanks!

Steelcards
Community Member

Same issue, just started...not able to find any answers

BirchHill
Community Member

This is great. No one from Nest or Google replies to anything here.

BirchHill
Community Member

I also had the same issue with a Sensi Smart thermostat. Had to tank it.  Don't want to buy a nest if it has the exact same problems as the Sensi. Guess Google expects you to buy products with zero support.

Spray
Community Member

Don’t buy nest. I seriously have an entire brand new home and furnace and the thing doesn’t work! I’m on my second replacement now after 5 visits from hvac asleep, I haven’t even lived here 90 days!!!! 

Diyx145
Community Member

I’ve had issues before but HVAC came 5 times to “fix” the issue. They changed a few things and it would work for a few hours and then die again. I think I may have solved one of the issues. It was my Taco control board.  I was able to start the boiler when flexing the board or pushing on one of the relays. It would fire and turn off the boiler. 

Old board was from 2007 and I’m assuming cracked some how. Put the new board in and also purchased the nest power adapter for each zone.  I don’t have common wires to my thermostats and at times had the battery issue. 

Boiler fires right up without cycle issues for a month now. It’s been cold and has been working fine. It used to have issues when multiple thermostats + hot water send requests altogether.  It would turn off and I’d have to cycle it on and off.

Not sure if it was the new board or the power adapters that are doing the trick. Played it safe and just did both. I’ll update if it cycles/clicks again. Good luck

BarnesR
Community Member

Still short cycling. Seems to occur first cycle in the morning when it is below 40 outside. Rheem RGDG gas forced air. Tried the following with no improvement: Cleaned flame sensor, replaced flame sensor, replaced furnace control board, disconnected blue "C" wire.

Now testing with Y1 wire disconnected, C wire reconnected. Working so far. I read someone resolved their short cycle issue by setting the mode to "heat+cool" (with cool temp set high so AC will never turn on). I will try this next if removing the Y1 wire fixes my issue. Can't just leave off the Y1 wire permanently or the air conditioner will not function this summer. If neither fixes the problem we will reinstall the old school thermostat.

The Nest thermostat worked fine for a couple years before, it seems to have started malfunctioning after we added central air to the furnace? Or maybe after some update a few months ago?

BarnesR
Community Member

I can confirm our short cycling problem does not occur when "heat+cool" mode is selected (cooling set to 90 to prevent AC from running). Google support told me they have no way to report this reproducible issue to a software engineer.

Removing the Y1 wire also fixes the problem  but this makes the AC inoperable 

BarnesR, I've been having short cycling issues with my gas heating. I called tech support and the tech had me remove the C wire inside my thermostat. The heat hasn't kicked back on yet so I don't know if that did anything.  Additionally, when the heat short-cycled and finally reached the set temperature, the actual home temperature reading shot up about 2 to 3 degrees warmer than what I had set the temperature for.  So, it's like the thermostat couldn't tell read the correct ambient temperature in addition to the short cycling.

By changing the mode to heat+cool, did it make any difference if the c wire was connected or not? Right now, mine is set only to heat mode and no c wire is connected. 

It did still short cycle with the C wire disconnected. The short cycling is still occurring at times, with or without the C wire, with or without the Y1 wire, and in heat only or heat+cool mode. If I set the mode to "off" for an hour or so, it will always short cycle when the heat is first turned back on. Then it will work normally. I think the schedule also is causing short cycling when the schedule first turns on the heat. Then it will work normally for the rest of the day.

Today I plan to install off delay relays between the Nest thermostat and the furnace control board. The idea is the relays will keep the furnace running if the Nest momentarily drops out doing it's "power stealing" thing. I'll let you know if this works out.

BarnesR
Community Member

I installed "off delay" relays to see if that would keep the furnace running in case the Nest was dropping out temporarily. The situation did not change, proving the Nest thermostat is not causing the short cycling trouble with our furnace. The issue occurs intermittently. Trying different things with the Nest wiring and mode seems to help at first, but the trouble always eventually started again. I will continue troubleshooting the furnace...

BarnesR
Community Member

Finally cured our short cycling problem. Was blaming the Nest but it was the furnace all along. Intermittent problem seemed to get better after messing with Y1 or C wire, or mode setting. But short cycling would eventually start again. We found a loose connection in a wire connector where it plugs into the control board. It was the wire going to the flame sensor. It would only fail when the furnace was cold, after being off for an hour or more. Pulled the connection off the control board and twisted it around 360 degrees before plugging back in. This temporarily fixed the intermittent connection in the orange wire.

PXL_20221204_223714042.jpg

BarnesR,

 

Since the repair has your furnace been operating correctly? In a strange coincidence, I had to change my Nest mode from 'heat' to 'heat and cool'. Sure enough, there have been no short cycling issues at all. It's been nearly a week since I changed modes.

There may be 2 issues with our furnace: 1) flame goes out within a few seconds after lighting (and yellow flame sense LED does not turn on when flame is present); or 2) flame starts OK and yellow LED lights but flame turns off as soon as the blower kicks on.

Mostly it does #2, and eventually stays running after 1 or 2 retries. But the other night it was consistently doing #1 and locking out. Ammeter test showed no current from flame sensor. Kept doing this until I unplugged the P1 connector on the control board, twisted the wiring, and plugged it back in. Worked for almost a week before starting #2 again. Yesterday I ran a new flame sensor wire from P1 directly to the flame sensor, bypassing an inline connector. So far so good. If the problem returns I will look at other wires in the P1 connector, a poor connection in any of those wire might be causing this intermittent problem.