STEP
ACTION
YES
NO
GO TO
24
Do you have continuity between the ORANGE wire con-
nected to the low heat pressure switch LPS and chassis
ground?
25
3
25
The ORANGE wire from low heat pressure switch LPS is
shorting to ground. Replace or repair it.
11
26
Does status code 24 begin flashing when the gas valve GV
is energized?
27
17
27
Disconnect jumper wire across R and W/W1 thermostat ter-
minals and replace secondary voltage fuse.
28
28
Disconnect BLUE wire to gas valve GV and jumper R and
W/W1 thermostat terminals.
29
29
Does status code 34 flash? If not, status code 24 should
occur when BLUE wire is energized.
33
30
30
Turn power off and disconnect PL1 from variable speed fur-
nace control.
31
31
Do you have continuity between the BLUE wire and chassis
ground?
32
3
32
The BLUE wire to gas valve GV is shorting to ground. Re-
place or repair it.
11
33
Replace gas valve GV.
4
34
Turn power off and disconnect PL1 from variable speed fur-
nace control.
35
35
Do you have continuity between the GRAY wire connected
to the high heat pressure switch HPS and chassis ground?
36
3
36
You have a short circuit in the high heat pressure switch
circuit.
11
37
Reconnect the pressure tube from the pressure switch as-
sembly back to the collector box.
38
38
Does status code 24 begin flashing when the high heat
pressure switch HPS is energized?
39
56
39
Disconnect jumper wire across R, W/W1, and W2 thermo-
stat terminals and replace secondary voltage fuse.
40
40
Disconnect BROWN wire to gas valve GV and jumper R,
W/W1, and W2 thermostat terminals.
41
41
Does status code 24 begin flashing when the high heat
pressure switch HPS is energized?
42
33
42
Turn power off and disconnect PL1 from variable speed fur-
nace control.
43
43
Do you have continuity between the BROWN wire and
chassis ground?
44
3
44
The BROWN wire to high heat pressure switch HPS and
gas valve GV is shorting to ground. Replace or repair it.
11
45
Disconnect jumper wire across R, W/W1, and W2 thermo-
stat terminals and wait until blower stops.
46
46
Jumper R, G, and Y/Y2 thermostat terminals.
47
47
Does status code 24 begin flashing when G and Y/Y2 are
energized?
3
48
48
Reconnect all thermostat leads (except humidifier lead to
HUM terminal) to variable speed furnace control and oper-
ate furnace in heating and cooling mode from thermostat.
49
49
Does status code 24 occur during heating cycle?
50
51
50
You have a defective thermostat or a short circuit in R,
W/W1, or W2 wiring between thermostat, furnace, and out-
door unit. If the furnace is twinned, also check the twinning
kit relay TKR.
11
51
Does status code 24 occur during cooling cycle?
52
53
52
You have a defective thermostat, short circuit in G, Y1,
Y/Y2 or O wiring between thermostat and outdoor unit, or a
short circuit in the outdoor unit contactor or reversing valve-
(heat pump only).
11
53
Does problem usually occur in cooling mode?
54
55
54
Check outdoor unit contactor. Failure to pull in can cause
excessive current draw on low-voltage circuit. This can be
an intermittent problem.
11
55
Reconnect humidifier and check for excessive current draw
when the blower turns ON. If current draw is excessive
check wiring to humidifier solenoid, diode bridge(if used),
and humidifier solenoid.
11
19
