Heil, Tempstar 97CMN Series Fault Codes

Skylar Kaczanowski

Mar 23, 2025

Here are the error codes on the Tempstar and Heil *97CMN Series Furnaces.

(F/G)97CMN Fault Codes
Code	Description	Recommended Action
10.1	L1 POLARITY FAULT	Rapid flash LED.
10.2	Refrigerant leak detected, operate blower.	Operate blower.
12.1	“W” ON at power up – Normal operation.	Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W closed) or when (R-W opens) during the blower on-delay period.
13.1	LIMIT CIRCUIT LOCKOUT	Lockout occurs if the limit, draft safeguard, flame rollout, or blocked vent switch*(if used) is open longer than 3 minutes. Control will auto-reset after 3 hours.
14.1	IGNITION LOCKOUT	System failed to ignite gas and prove flame in 4 attempts. Control will auto-reset after 3 hours.
14.2	FLAME LOST	3 times after 70s of heating.
14.3	LOCKOUT	7 loss of flame events during a heat request.
14.4	LOCKOUT	7 pressure switch open events during a heat request.
15.1	BLOWER RPM LOCKOUT	Lockout occurs when no blower rpm is detected.
15.2	LOCKOUT	Failed to reach 500 rpm during startup. Check for loose blower wire connections or failed blower motor.
21.1	24VAC sensed on gas valve when it shouldn’t be.	Turn off power and wait 5 minutes to retry. Check for stuck closed gas valve relay on control or miswire/short at gas valve wire.
22.1	Stuck open or leaky gas valve.
23.4	LPS pressure switch	Check for obstructed pressure tube or a pressure switch stuck closed.
23.5	HPS pressure switch	Check for obstructed pressure tube or a pressure switch stuck closed.
23.6	MPS pressure switch	Check for obstructed pressure tube or a pressure switch stuck closed.
24.1	FUSE FAULT	Check for short circuit in secondary voltage (24-V) wiring, including thermostat leads. Disconnect thermostat leads to isolate short circuit.
25.1	NO PROGRAM info in micro, no heating operation.	Reprogram control.
25.2	CORRUPTED PROGRAM FILE	Reprogram control using service app or super plug (supplied separately).
25.4	MAIN PROGRAM INVALID	Using backup program to operate. Reprogram control to correct issue. Control still operates normally.
25.5	INSTALLER SETTINGS CORRUPTED	Try reselecting installer settings, or reprogram control. Control will operate using default installer settings.
25.6	WRONG PROGRAM for control used	Reprogram control so program matches control used. No heating operation. If program in furnace control is missing, not recognized, or corrupted. Reprogram control with correct program # as listed on the rating plate. Replace control if issue remains.
27.1	Program in super plug is missing, not recognized, or corrupted.	Remove super plug, then retry. If still have 27 code, try a different super plug. If still fails, replace control.
27.2	Program in super plug is missing, not recognized, or corrupted.	Remove super plug, then retry. If still have 27 code, try a different super plug. If still fails, replace control.
27.3	Program in super plug is missing, not recognized, or corrupted.	Remove super plug, then retry. If still have 27 code, try a different super plug. If still fails, replace control.
31.1	Medium heat pressure switch input OFF when it should be ON
31.2	Medium heat pressure switch input ON when it should be OFF
31.6	Open HPS – HPS failed to close in 75s when transitioning from low to high heat	Check for excessive wind, restricted vent, defective inducer motor, low inlet gas pressure (if LGPS used), inadequate combustion air supply, proper vent sizing, disconnected/obstructed pressure tubing, condensate drainage blocked or restricted.
51.1	OAT OPEN – Outdoor Air Temperature sensor connection is open	Check for loose connection at control board screw terminals.
51.2	OAT SHORT – Outdoor Air Temperature sensor wires are shorted	Check for loose connection at control board screw terminals.
32.2	OPEN MAIN PRESSURE SWITCH	If LPS is open longer than 5 minutes or has reopened, inducer shuts off for 15 minutes before retry.
52.1	SAT OPEN – Supply Air Temperature sensor connection is open	Check for loose connection at control board screw terminals.
52.2	SAT SHORT – Supply Air Temperature sensor wires are shorted	Check for loose connection at control board screw terminals.
33.1	A SWITCH HAS OPENED IN THE MAIN LIMIT	Indicates the limit or flame rollout is open. Blower will run for 4 minutes or until open switch remakes, whichever is longer.
53.1	RAT OPEN – Return Air Temperature sensor connection is open	Check for RAT firmly plugged into control board, damaged RAT sensor, dirty filter, or restricted duct system.
53.2	RAT SHORT – Return Air Temperature sensor is shorted	Check for RAT firmly plugged into control board, damaged RAT sensor, dirty filter, or restricted duct system.
41.2	NO BLOWER RPM – No blower rpm when blower motor is running	Check for loose blower wire connections, failed blower motor.
41.3	Failed to reach 500rpm at startup	Check for loose blower wire connections or failed blower motor.
42.1	No inducer RPM at startup
42.2	No RPM when inducer motor is running
42.3	Exceeding inducer RPM limit
43.1	HPS closed before LPS
45.1	CONTROL FAILURE – flame circuit fault, memory mismatch or sequence error	Replace control.
45.2	CONTROL FAILURE – gas valve relay will not close	Replace control.
45.3	CONTROL FAILURE – EEPROM memory issue	Replace control.
45.4	CONTROL FAILURE – Micro loss of Comm	Replace control.
34.1	IGNITION FAULT – During four consecutive ignition trials.	Check for gas valve turned off, manual shut-off valve, green/yellow wire connection, or flame sensor grounding.
34.5	AFTER SUCCESSFUL IGNITION (flame proven) Low heat flame loss before heating blower on delay.
34.6	AFTER SUCCESSFUL IGNITION (flame proven) High heat flame loss before heating blower on delay.
34.7	AFTER SUCCESSFUL IGNITION (flame proven) Low flame loss after heating blower on delay.
34.8	AFTER SUCCESSFUL IGNITION (flame proven) Low flame loss after heating blower on delay.
35.1	Modulating gas valve not communicating.