KeepRite Error Code 81: Low stage thermal lockout (AC)

Updated October 13, 2026 · by Aurora Star Tech Inc.

KeepRite error code 81 on a air conditioner means: Low stage thermal lockout. It is also called KeepRite diagnostic code 81.

High severityAir ConditionerAlso Heat PumpKeepRite *CA/*CH Two-Stage Communicating

Homeowner? What KeepRite code 81 means for you

Call a technician Your air conditioner is reporting: Low stage thermal lockout. The air conditioner 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.
Check both breakers and the outdoor disconnect box beside the outdoor unit; all should be ON.
Look at the air filter. If it is grey and clogged, replace it; a blocked filter causes many shutdowns.
Keep about 2 feet around the outdoor unit clear of leaves, grass and debris.
If you see ice on the pipes or the indoor coil, turn the system off and run only the fan for a few hours, then call a technician.
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) 657-2977 Book a service call

Licensed technicians serving Vaughan, Toronto and the GTA.

What does KeepRite error code 81 mean?

Thermal cutout on 3 cycles in a row; low stage locked out 4 hours or until 24 V is cycled.

Applies to: KeepRite *CA7/*CA9 AC and *CH6/*CH9 HP two-stage communicating

Common causes of KeepRite code 81

Repeated low-stage overload trips - see code 71

Safety: Gas, electrical and refrigerant work must be done by a licensed technician. Turn off power and gas before servicing, never bypass a safety control, and always follow the manufacturer's manual for your exact model.

KeepRite models that use code 81

*CA624 *CA636 *CA648 *CA660 *CA924 *CA936 *CA948 *CA960

Other KeepRite AC codes

Code	Meaning
55	Outdoor coil sensor fault
56	Air and coil sensors disagree
71	Low stage thermal cutout
72	Compressor thermal cutout (two-stage: high stage)
73	Contactor stuck closed
74	No 230 V at compressor
82	Thermal lockout (two-stage: high stage)
83	Low pressure lockout
84	High pressure lockout
Red TRIP LED	Comfort Alert TRIP - Y call but compressor not running
TRIP + ALERT flashing together	Comfort Alert - control voltage too low to operate

All KeepRite Air Conditioner error codes →

KeepRite code 81: homeowner questions

What does KeepRite code 81 mean?

Low stage thermal lockout. Thermal cutout on 3 cycles in a row; low stage locked out 4 hours or until 24 V is cycled.

Is it safe to keep using my air conditioner with code 81?

It depends on the cause. The air conditioner 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 KeepRite code 81 myself?

You can try one reset (power off for 30 seconds, then on). If KeepRite code 81 comes back, the cause is still there and a licensed technician should check it.

Who can fix KeepRite code 81 near me?

Aurora Star Tech Inc. repairs KeepRite air conditioners in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.

Homeowner help: AC Running But Not Cooling: What to Check

Troubleshooting guides

Not cooling All brands · Air Conditioner
Checking OAT and OCT thermistors - KeepRite C4A3/CXA6 KeepRite · Air Conditioner

Source: KeepRite_ICP_KeepRite_Tempstar_Heil_split_A_C_HP_R_410A_R_22_service_421_08_5400_04.txt - section Table 17 Troubleshooting (two-stage). 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.