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STEP
15.
Replace variable speed furnace control.
16.
Is the low heat pressure switch LPS wired correctly?
17.
Replace the pressure switch assembly.
18.
Is the high heat pressure switch HPS wired correctly?
19.
Rewire high heat pressure switch HPS per wiring diagram.
20.
Replace the pressure switch assembly and replace the variable speed furnace control.
21.
Check the inducer PWM line. To do this disconnect PL11 from the inducer motor and
connect a DC voltmeter across terminals PL11- -2 BROWN (+) and PL11- -10 YELLOW (- -)
then run COMPONENT TEST by turning setup switch SW1- -6 ON. Does voltage across
PL11- -2 and PL11- -10 change between states as shown below?
- - State 1 – OFF (1.0 – 4.0 vdc)
- - State 2 – MED (7.0 – 10.0 vdc)
22.
Replace inducer motor or inducer motor assembly.
Status Code 24
SECONDARY VOLTAGE FUSE IS OPEN - - Indicates fuse is open and there is a short in low- -voltage wiring.
STEP
1.
Turn power off and remove the blower access panel.
2.
Is secondary voltage fuse blown? Check continuity to make sure.
3.
Replace variable speed furnace control.
4.
Replace secondary voltage fuse if necessary then go to page number indicated in Index for
CLEANUP AND START- -UP INSTRUCTIONS.
5.
Disconnect all thermostat leads from the variable speed furnace control (including all wires
connected to the HUM terminal) and replace secondary voltage fuse.
6.
Turn power on and depress door switch. Use a piece of tape to hold switch closed.
7.
Does status code 24 flash?
8.
Turn power off and disconnect PL1 from variable speed furnace control.
9.
Do you have continuity between either RED wire connected to the limit circuit and chassis
ground?
10.
You have a short circuit in the limit switch circuit. This includes limit switch LS, and flame
roll- -out switch FRS.
11.
Fix problem.
12.
Disconnect the pressure tube from the collector box and jumper R and W/W1 thermostat
terminals.
13.
Does status code 24 begin flashing when W/W1 is energized?
14.
Turn power off and disconnect PL1 from variable speed furnace control.
15.
Do you have continuity between the YELLOW wire connected to the low heat pressure
switch LPS and chassis ground?
16.
You have a short circuit in the low heat pressure switch circuit.
17.
Does status code 24 begin flashing when the HUM terminal is energized?
Note: On the variable speed furnace control the HUM terminal is energized when the
blower turns ON.
18.
Disconnect jumper wire across R and W/W1 thermostat terminals and wait until inducer
stops.
19.
Disconnect the pressure tube from the collector box and jumper R, W/W1, and W2 thermo-
stat terminals.
20.
Does status code 24 begin flashing when W/W1 is energized?
21.
Reconnect the pressure tube from the pressure switch assembly back to the collector box.
22.
Does status code 24 begin flashing when the low heat pressure switch LPS is energized?
23.
Turn power off and disconnect PL1 from variable speed furnace control.
24.
Do you have continuity between the ORANGE wire connected to the low heat pressure
switch LPS and chassis ground?
25.
The ORANGE wire from low heat pressure switch LPS is shorting to ground. Replace or
repair it.
26.
Does status code 24 begin flashing when the gas valve GV is energized?
ACTION
ACTION
16
YES
NO
GO TO
7
17
12
7
20
19
7
7
22
15
7
YES
NO
GO TO
2
5
3
4
INDEX
6
7
8
12
9
10
3
11
4
13
14
21
15
16
3
11
3
18
19
20
34
37
22
23
26
24
25
3
11
27
17
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