STEP
ACTION
YES
NO
GO TO
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 prop-
erly aligned?
27
24
27
Remove tape from door switch, turn power off at main dis-
connect, 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 re-
striction. 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 set thermostat to OFF position. 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
7
Go to page number indicated in the Index for the section
covering the status code.
INDEX
8
Remove blower access panel and depress door switch. Use
a piece of tape to hold switch closed.
9
9
Jumper R and W/W1 thermostat terminals.
10
10
Does status code 21 start flashing when the low heat pres-
sure switch LPS makes?
11
12
11
Replace the variable speed furnace control.
5
16
