- 15 -
STEP ACTION YES
NO
GO
TO
19.
Replace flame rollout switch FRS.
10
20.
Reset flame rollout switch FRS, turn power on, and observe furnace operation for (2) 15
minute cycles.
21
21.
Does the flame rollout switch FRS trip again?
23
22
22.
Does a different status code flash?
5
10
23.
You have inadequate combustion-air supply. This may be caused by:
- Reversed vent and combustion-air pipes.
- Poor burner, manifold, or orifice alignment.
- Blocked heat exchanger.
- Leak somewhere between primary and secondary heat exchangers.
- Leak in secondary heat exchanger.
24
24. Fix
problem
10
25.
You have an open RED wire or bad terminal in limit circuit. Repair wire or replace harness.
10
26.
Does furnace have the proper limit switch, limit shield, blower baffle (if used), and rear air
baffle (if used)? If so, are the limit switch, limit shield, and heat exchangers properly aligned?
27 24
27.
Remove tape from door switch, turn power off at main disconnect, and remove jumper across
R and W/W1.
28
28.
Is blower wheel firmly mounted on motor shaft?
29
24
29.
Does the model plug PL4 match the part number specified on the Model Plug Chart in upper
left hand corner of wiring schematic?
31 30
30.
Replace model plug.
10
31.
Lockout may have been caused by excessive return-air restriction. Check all dampers, filters,
and return-air grilles for blockage. Add more return-air openings if necessary. Use Appendix
D to evaluate external static pressure. Reference status code 33 for additional troubleshooting
steps.
10
Status Code 14
IGNITION LOCKOUT - This status code indicates the furnace failed to ignite gas and/or prove flame in 4 attempts. The variable
speed furnace control will auto-reset in 3 hours. If the inducer motor is not running during lockout refer to status code 34.
If the inducer motor is running at full speed during lockout this indicates that flame sense was lost 3 times within 60 minutes of
cumulative gas valve operating time after the gas valve was already ON for 70 seconds. It is usually caused by flame rollout
that causes loss of flame sense before the flame rollout switch can trip.
Status Code 15
BLOWER MOTOR LOCKOUT - This status code indicates the blower failed to reach 250 RPM or the blower failed to
communicate to the variable speed furnace control within 30 seconds after being turned ON in two successive heating cycles.
Control will auto reset after 3 hours. Refer to status code 41.
Status Code 21
GAS HEATING LOCKOUT - This status code indicates the main gas valve relay MGVR on the variable speed furnace control is
stuck closed or there is a miswire/short to gas valve wiring. Make sure the BLUE wire goes to the gas valve M terminal and the
GREEN/YELLOW wire goes to the gas valve C terminal. The variable speed furnace control will NOT auto-reset.
STEP ACTION YES
NO
GO
TO
1.
Turn power off and disconnect User Interface ABCD connector (if used) or the R thermostat
lead (if used) from the furnace control board. Then turn power back on.
2
2.
Does status code 21 flash?
3
6
3.
There is a miswire or short to gas valve wiring.
4
4. Fix
problem
5
5.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
INDEX
6.
Does a different status code flash?
7
8
