Status Code 24 - Secondary Voltage Fuse Is Open - Bryant 355CAV A Series Troubleshooting Manual

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 User Interface ABCD connector (if used), or all thermostat leads (if used) 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 YELLOW wire to the low heat pressure switch LPS.
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. Jumper R, W/W1, and W2 thermostat terminals.
20. Disconnect jumper wire across R and W/W1 thermostat terminals and wait until inducer stops.
21. Reconnect the pressure tube from the pressure switch assembly back to the collector box.
22. Jumper R and W/W1 thermostat terminals.
23. Does status code 24 begin flashing before the hot surface igniter HSI is energized?
24. Turn power off and disconnect PL1 from variable speed furnace control.
25. Do you have continuity between the ORANGE wire connected to the low heat pressure switch
LPS and chassis ground?
26. The ORANGE wire from low heat pressure switch LPS is shorting to ground. Replace or
repair it.
27. Disconnect the VIOLET wire from the throttling valve TV.
28. Do you have continuity between the VIOLET wire connected to the medium heat pressure
switch MPS and chassis ground?
29. The VIOLET wire from medium heat pressure switch MPS is shorting to ground. Replace or
repair it.
30. Replace the valve train assembly. The valve train assembly includes the gas valve GV and the
throttling valve TV. The throttling valve TV is not a serviceable part by itself.
31. Does status code 24 begin flashing when the gas valve GV is energized?
32. Disconnect jumper wire across R and W/W1 thermostat terminals and replace secondary
voltage fuse.
33. Disconnect BLUE wire to gas valve GV and jumper R and W/W1 thermostat terminals.
34. Does status code 34 flash? If not, status code 24 should occur when BLUE wire is energized.
35. Turn power off and disconnect PL1 from variable speed furnace control.
36. Do you have continuity between the BLUE wire and chassis ground?
37. The BLUE wire to gas valve GV is shorting to ground. Replace or repair it.
38. Replace gas valve GV.
ACTION
- 19 -
YES NO GO TO
2
5 3
4
INDEX
6
7
8 12
9
10 3
11
4
13
14 20
15
16 39
11
3 18
19
41
21
22
23
24 31
25
26 27
11
28
29 30
11
4
32 17
33
34
38 35
36
37 3
11
4