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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22515
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a carrier furnace, my furnace will turn on and work

Customer Question

I have a carrier furnace, my furnace will turn on and work properly bringing the room temperature to the desired one. Although once it stops once it hit the temperature needed, it won't start back on and sometimes it shows one blink followed by two quick blinks. Also at times it will show three slow blinks followed by three quick blinks. What could be wrong with it? I checks all the buttons that could be reseted but it keeps doing the same.
Submitted: 1 year ago.
Category: HVAC
Expert:  HVAC Guru replied 1 year ago.

Hello and thanks for using this service, if you have been waiting do not worry or get upset I am just one of the techs on here and I try to get to as many customers as I can and I just picked up your question now.

That is a 33 error meaning one of the rollout thermostat around the burner area have tripped open. Can you look around the burner area for these thermostats. Most have a reset button between the two wires that go to the thermostat that you can press in to reset them and others may not. One of them is reading open so the board is displaying that error code for you. The unit has overheated and tripped one or one may just have gone bad. Also check the filter and make sure it is clear as that can cause the unit to overheat and cause them to trip.

We are on the honor system for our time, all I ask is please rate my service using the STAR RATING LINK on your page before you leave. If you are not happy with the service please let me know before leaving a negative rating. This is the only way I am paid or credited through the site for my time. This will also allow you to get directly back to me for FREE follow up questions and tips are greatly appreciated! Thanks

Expert:  HVAC Guru replied 1 year ago.

You can put the wires together to each one to bypass each one and try it as some may not have a reset button on them.

Expert:  BillyHvac replied 1 year ago.


It cannot be the rollout as they would need a manual reset. You say it comes and goes so this means the high limit is tripping. This can be from lack of air flow such as plugged filter, dirty blower motor wheel, duct work restricted...and also Bryant/Carrier/Payne had a issue with circuit boards HK42FZ not running the blower reliably.

First we need to check any air flow issues. Then if 33 is still present we want to check the limit which is a credit card sized flat plate on the front wall of the furnace behind the gas valve. This is not a button has to cool down to close..and if stuck sometimes tapping the switch helps.

So forget the rollouts and look at the limit on front wal...and anything that can impede air flow.


Customer: replied 1 year ago.
I checked all vents and air is flowing throughly with all vents open, exhaust is clear & working fine. Althoiugh I did not see that card sized board behind the gas valve.
Expert:  BillyHvac replied 1 year ago.

If no plate then you have a oval plate with a round switch and 2 wires attached..if you see this tap it a few times and tell me if code changes