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58SU0A (Series 2 & 3): Troubleshooting Guide
Status Code 24 - Secondary Voltage Fuse Open
Indicates fuse is open and/or 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 furnace control.
Replace secondary voltage fuse, if necessary, then go to page number indicated in Index for
4.
CLEANUP AND START-UP INSTRUCTIONS.
Disconnect all thermostat leads from the furnace control board, including all wires connected to the
5.
HUM terminal
6.
Replace the fuse, 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 the transducer PL3 connection on the furnace control.
9.
Replace the fuse, turn power on.
10.
Does status code 24 flash?
11.
Turn power off and disconnect the transducer PL12 connection at the transducer.
12.
Do you have continuity between the red wire (PL12-1) or the black wire (PL12-3) and chassis ground?
13.
Replace transducer
14.
You have a short to ground in the red or black transducer wiring. Repair or replace harness
15.
Turn off power and Reconnect transducer connection PL3 at furnace control
16.
Disconnect PL1 from furnace control.
Do you have continuity between either RED wire (PL1-6 or PL1-8) connected to the limit circuit and
17.
chassis ground?
You have a short circuit in the limit switch circuit. This includes limit switch(es) LS, Draft safeguard
18.
switch (DSS), Burner Thermal switches (BTS), and Auxiliary limit switches (ALS)
19.
Fix problem.
20.
Jumper R and W thermostat terminals.
21.
Does status code 24 begin flashing immediately when W is energized?
22.
Does status code 24 begin flashing when the gas valve GV is energized?
23.
Disconnect jumper wire across R and W thermostat terminals and replace secondary voltage fuse.
24.
Disconnect BLUE wire to gas valve GV and jumper R and W thermostat terminals.
25.
Does status code 34 flash? If not, status code 24 should occur when BLUE wire is energized.
26.
Turn power off and disconnect PL1 from furnace control.
27.
Do you have continuity between the BLUE wire and chassis ground?
28.
The BLUE wire to gas valve GV is shorting to ground. Replace or repair it.
29.
Replace gas valve GV.
Does status code 24 begin flashing when the HUM terminal is energized?
30.
NOTE: On the furnace control the HUM terminal is energized when the blower turns ON.
31.
Continue to observe the furnace operation for 10 minutes.
32.
Does status code 24 flash after the blower comes on?
33.
The insulation is loose and has shorted against the limit switch(es).
34.
Check for loose or torn insulation because it can cause intermittent occurrences of status code 24.
35.
Disconnect jumper wire across R and W terminals and wait until inducer stops.
36.
Jumper R, G, and Y thermostat terminals.
37.
Does status code 24 begin flashing when G and Y are energized?
Reconnect all thermostat leads to the furnace control board. Do NOT reconnect the humidifier lead to
38.
the HUM terminal. Operate the furnace in heating and cooling modes from the thermostat
39.
Does status code 24 occur during heating cycle?
You have a defective thermostat or a short circuit in R, W/W1, or W2 wiring between thermostat, User
40.
Interface, furnace, and outdoor unit. If the furnace is twinned, also check the twinning kit relay TKR.
41.
Does status code 24 occur during cooling cycle?
You have a defective thermostat, short circuit in G, Y1, Y/Y2 or O wiring between thermostat and
42.
outdoor unit, or a short circuit in the outdoor unit contactor or reversing valve (heat pump only).
43.
Does problem usually occur in cooling mode?
Check outdoor unit contactor. Failure to pull in can cause excessive current draw on low-voltage circuit.
44.
This can be an intermittent problem.
Reconnect humidifier and check for excessive current draw when the blower turns ON. If current draw
45.
is excessive check wiring to humidifier and humidifier valve solenoid
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
ACTION
15
YES
NO
GO TO
2
5
3
4
INDEX
6
7
8
20
9
10
15
11
12
14
13
16
17
18
3
19
4
21
3
22
23
30
24
25
29
26
27
28
3
19
19
3
31
32
33
34
35
36
37
3
38
39
36
41
19
42
43
19
44
45
19
19
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