KeepRite Error Code 81: Low stage thermal lockout (Heat Pump)

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

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

High severityHeat PumpKeepRite *CA/*CH Two-Stage Communicating

Homeowner? What KeepRite code 81 means for you

Call a technician Your heat pump is reporting: Low stage thermal lockout. The heat pump 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.
In winter, keep snow and ice off and away from the outdoor unit. A short defrost cycle with steam is normal.
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

*CH624 *CH636 *CH648 *CH660 *CH924 *CH936 *CH948 *CH960

Other KeepRite Heat Pump 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
Phase monitor LED flashing	3-phase monitor - phase reversal

All KeepRite Heat Pump 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 heat pump with code 81?

It depends on the cause. The heat pump 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 heat pumps 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 · Heat Pump Not Heating or Blowing Cold Air

Troubleshooting guides

Forcing a defrost to test the board - KeepRite N4H4/R4H4/WCH4/NXH5 KeepRite · Heat Pump
Outdoor unit will not run or will not defrost - KeepRite heat pump defrost board (FAST 1173636/1177927/1190281) KeepRite · Heat Pump

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.