Carrier 58MVP Troubleshooting Manual page 19

OUTDOOR UNIT CAPACITY
A/C Setting
CF Setting
Fault 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 blower access panel.
2. Is secondary voltage fuse blown? Check continuity to make sure.
3. Replace furnace control board.
Go to page number indicated in Index for CLEANUP AND START-UP
4.
INSTRUCTIONS.
Disconnect all thermostat leads from furnace control board (including HUM ter-
5.
minal) and replace secondary voltage fuse.
6. Depress door switch. Use a piece of tape to hold switch closed.
7. Does Fault Code 24 flash?
You have a short circuit in limit switch circuit. This includes limit switch, flame
8.
rollout switch, and auxiliary limit switch.
9. Fix problem and replace secondary voltage fuse if necessary.
10. Jumper R and W/W1 thermostat terminals on furnace control board.
11. Does Fault Code 24 occur when W/W1 is energized?
Disconnect jumper wire across R and W/W1 thermostat terminals and replace
12.
secondary voltage fuse.
Disconnect PL2 from furnace control board and jumper R and W/W1 thermostat
13.
terminals on furnace control board.
14. Does Fault Code 24 occur when W/W1 is energized?
15. You have a short circuit in pressure switch circuit.
16. Does Fault Code 24 occur when low-pressure switch is energized?
17. Disconnect PL2 from furnace control board.
Do you have continuity between the N.O. (Normally Open) contact on low-
18.
pressure switch LPS and chassis ground?
The ORANGE wire from low-pressure switch LPS is shorting to ground. Re-
19.
place or repair it.
20. Does Fault Code 24 occur when gas valve GV is energized?
Disconnect jumper wire across R and W/W1 thermostat terminals and replace
21.
secondary voltage fuse.
Disconnect BLUE wire to gas valve GV and jumper R and W/W1 thermostat
22.
terminals on furnace control board.
Does Fault Code 34 IGNITION PROVING FAULT occur? If not, Fault Code 24
23.
should occur when BLUE wire is energized.
24. Disconnect PL1 from furnace control board.
25. Do you have continuity between BLUE wire and chassis ground?
26. The BLUE wire to gas valve GV is shorting to ground. Replace or repair it.
27. Replace gas valve GV.
28. Add a jumper across R and W2 thermostat terminals on furnace control board.
29. Does Fault Code 24 occur when high-pressure switch HPS is energized?
Disconnect jumper wire across R, W/W1, and W2 thermostat terminals and re-
30.
place secondary voltage fuse.
Disconnect BROWN wire to gas valve GV and jumper R, W/W1, and W2 ther-
31.
mostat terminals on furnace control board.
32. Does Fault Code 24 occur when high-pressure switch HPS is energized?
33. Disconnect PL1 from furnace control board.
34. Do you have continuity between BROWN wire and chassis ground?
35. The BROWN wire to gas valve GV is shorting to ground. Replace or repair it.
36. Disconnect PL2 from furnace control board.
Do you have continuity between the N.O. (Normally Open) contact on high-
37.
pressure switch HPS and chassis ground?
The BROWN wire from high-pressure switch HPS is shorting to ground. Re-
38.
place or repair it.
Disconnect jumper wire across R, W/W1, and W2 thermostat terminals and wait
39.
until blower stops.
Table 4—Two-Speed AC/HP Airflow Requirements (CFM)
036
3 Tons—1200
800
048
4 Tons—1600
1000
19
060
5 Tons—2000
1000
YES NO GO TO
— — 2
5 3 —
— — 4
— — INDEX
— — 6
— — 7
8 10 —
— — 9
— — 4
— — 11
12 16 —
— — 13
— — 14
3 15 —
— — 9
17 20 —
— — 18
19 3 —
— — 9
21 28 —
— — 22
— — 23
27 24 —
— — 25
26 3 —
— — 9
— — 4
— — 29
30 39 —
— — 31
— — 32
33 27 —
— — 34
35 36 —
— — 9
— — 37
38 3 —
— — 9
— — 40