Carrier Error Code 33.1: Main limit circuit switch open (Furnace)
Carrier error code 33.1 on a furnace means: Main limit circuit switch open. It is also called Carrier diagnostic code 33.1.
Homeowner? What Carrier code 33.1 means for you
Call a technician Your furnace is reporting: Main limit circuit switch open. The furnace has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Safe things you can check yourself
- Check the thermostat: right mode (Heat or Cool), set a few degrees past room temperature, and fresh batteries if it uses them.
- Make sure the unit has power: its on/off switch (often looks like a light switch near the unit) is ON and the breaker in the electrical panel is not tripped.
- Make sure the furnace front door or panel is closed properly; many furnaces will not run with the door switch open.
- Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the gas valve next to the furnace is open (handle in line with the pipe). Do not force it.
- Try one reset: turn the power off for 30 seconds, then back on. If the code comes back, stop resetting and call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Carrier error code 33.1 mean?
A switch in the main limit circuit (auto-reset limit or a manual-reset rollout switch) has opened.
Applies to: Carrier 59SC6A
Common causes of Carrier code 33.1
- Restricted airflow (filter, ducts, registers)
- Airflow setting too low / high temperature rise
- Blower failure
A technician checks these and 2 other possible causes on site before replacing any part.
Carrier models that use code 33.1
59SC6A026M14--1059SC6A040M14--1059SC6A040M17--1259SC6A060M14--1259SC6A060M17--1659SC6A080M17--1659SC6A080M21--2059SC6A100M21--2059SC6A100M21--2259SC6A120M24--2259SC6A140M24--22
Other Carrier Furnace codes
All Carrier Furnace error codes →
Carrier code 33.1: homeowner questions
What does Carrier code 33.1 mean?
Main limit circuit switch open. A switch in the main limit circuit (auto-reset limit or a manual-reset rollout switch) has opened.
Is it safe to keep using my furnace with code 33.1?
It depends on the cause. The furnace has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset Carrier code 33.1 myself?
You can try one reset (power off for 30 seconds, then on). If Carrier code 33.1 comes back, the cause is still there and a licensed technician should check it.
Who can fix Carrier code 33.1 near me?
Aurora Star Tech Inc. repairs Carrier furnaces in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Furnace Not Turning On: What to Check · Furnace Blinking Light: What the Flash Codes Mean
Troubleshooting guides
- Blowing cold air All brands · Furnace
- No heat All brands · Furnace
- Short cycling All brands · Furnace
- Burners will not light or stay lit - Carrier 58SB0A/58SB1A Carrier · Furnace
- Furnace not responding to thermostat - Carrier 58SB0A/58SB1A Carrier · Furnace
Source: Carrier 59SC6A Installation, Start-up, Operating and Service Instructions, Fig. 60 Service Label p.54; Start-up caution p.55; Adjust Temperature Rise and Check Safety Controls p.58-61. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.