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STEP
ACTION
YES
NO
GO TO
17
Replace the pressure switch assembly.
7
18
Is the high heat pressure switch HPS wired correctly?
20
19
19
Rewire high heat pressure switch HPS per wiring diagram.
7
20
Replace the pressure switch assembly and replace the vari-
able speed furnace control.
7
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
15
22
Replace inducer motor or inducer motor assembly.
7
Status Code 24
SECONDARY VOLTAGE FUSE IS OPEN - Indicates fuse is open and there is a short in low-voltage wiring.
STEP
ACTION
YES
NO
GO TO
1
Turn power off and remove the blower access panel.
2
2
Is secondary voltage fuse blown? Check continuity to make
sure.
5
3
3
Replace variable speed furnace control.
4
4
Replace secondary voltage fuse if necessary then go to
page number indicated in Index for CLEANUP AND
START-UP INSTRUCTIONS.
INDEX
5
Disconnect all thermostat leads from the variable speed fur-
nace control (including all wires connected to the HUM ter-
minal) and replace secondary voltage fuse.
6
6
Replace the fuse, turn power on and depress door switch.
Use a piece of tape to hold switch closed.
7
7
Does status code 24 flash?
8
12
8
Turn power off and disconnect PL1 from variable speed fur-
nace control.
9
9
Do you have continuity between either RED wire connected
to the limit circuit and chassis ground?
10
3
10
You have a short circuit in the limit switch circuit. This in-
cludes limit switch LS, and flame roll-out switch FRS.
11
11
Fix problem.
4
12
Disconnect the pressure tube from the collector box and
jumper R and W/W1 thermostat terminals.
13
13
Does status code 24 begin flashing when W/W1 is ener-
gized?
14
21
14
Turn power off and disconnect PL1 from variable speed fur-
nace control.
15
15
Do you have continuity between the YELLOW wire con-
nected to the low heat pressure switch LPS and chassis
ground?
16
3
16
You have a short circuit in the low heat pressure switch cir-
cuit.
11
17
Does status code 24 begin flashing when the HUM terminal
is energized?
Note: On the variable speed furnace control the HUM termi-
nal is energized when the blower turns ON.
3
18
18
Disconnect jumper wire across R and W/W1 thermostat ter-
minals and wait until inducer stops.
19
19
Disconnect the pressure tube from the collector box and
jumper R, W/W1, and W2 thermostat terminals.
20
20
Does status code 24 begin flashing when W/W1 is ener-
gized?
34
37
21
Reconnect the pressure tube from the pressure switch as-
sembly back to the collector box.
22
22
Does status code 24 begin flashing when the low heat pres-
sure switch LPS is energized?
23
26
23
Turn power off and disconnect PL1 from variable speed fur-
nace control.
24
18