Carrier 58MVP Troubleshooting Manual page 21

STEP
Go to page number indicated in Index for CLEANUP AND START-UP
8.
INSTRUCTIONS.
9. Does fault occur within 5 sec after W/W1 is energized?
Do you have 24v between the N.O. (Normally Open) contact on high-pressure
10.
switch HPS and Com on furnace control board?
11. Replace furnace control board.
12. Is high-pressure switch HPS wired correctly?
13. Rewire high-pressure switch HPS per wiring diagram.
14. Replace pressure switch assembly.
Do you have 24v between connector terminal PL2-4 and Com on furnace con-
15.
trol board?
16. The main harness is miswired.
17. Fix problem.
18. Does fault occur during blower on delay period?
Turn power off and disconnect jumper wire across R and W/W1 thermostat ter-
19.
minals.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat
20.
terminals on furnace control board.
21. Does Fault Code 14 start flashing when high-pressure switch HPS makes?
22. The BLUE and GREEN wires to gas valve GV are reversed.
23. Does fault occur during low fire after blower turns on?
Turn power off and disconnect jumper wire across R and W/W1 thermostat ter-
24.
minals.
Connect 1 side of a slope manometer with a tee to collector box pressure tap.
25. Connect other side with a tee to gas valve air pressure fitting. Refer to pressure
check diagram in Appendix C.
Turn power on and wait several sec, then jumper R and W/W1 thermostat ter-
26.
minals on furnace control board.
Monitor slope manometer. Does pressure reading appear to be stable when
27.
fault occurs?
28. Check for a sag in vent pipe. If problem persists, replace inducer motor.
Disconnect jumper wire across R and W/W1 thermostat terminals and wait until
29.
blower stops.
30. Jumper R, W/W1, and W2 thermostat terminals on furnace control board.
Does high-pressure switch HPS make, then break several times at start of cycle
31.
before faulting out?
32. The problem is either a sag in vent pipe or a clogged drain trap or line.
33. Does fault occur before main burners ignite?
Do you have 24v between C (Common) on high-pressure switch HPS and Com
34.
on furnace control board?
The YELLOW wire to high-pressure switch HPS is not making good connection.
35.
Repair or replace it.
Do you have at least 1.90 in. wc pressure drop across heat exchangers when
fault occurs? Determine this by connecting 1 side of slope manometer with a
36.
tee to collector box pressure tap. Connect other side with a tee to gas valve air
pressure fitting. Refer to pressure check diagram in Appendix C.
37. Is inducer motor MTR1 rotating in direction indicated on inducer housing?
38. Replace inducer motor or inducer motor assembly.
39. Turn power off.
40. Is inducer wheel okay?
41. If possible, replace inducer wheel. Otherwise, replace inducer motor assembly.
42. Is there any frost build-up on combustion-air inlet?
The problem is caused by reversed vent and combustion-air pipes or some
43.
other moist air entering combustion-air pipe.
44. You have excessive restriction in combustion-air or vent pipe.
Turn power off and disconnect jumper wire across R, W/W1, and W2 thermo-
45.
stat terminals.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat
46.
terminals on furnace control board.
Do you have 24v between connector terminal PL2-4 and Com on furnace con-
47.
trol board when fault occurs?
48. Turn power off.
Do you have continuity across terminal PL2-4 and N.O. (Normally Open) con-
49.
tact on high-pressure switch HPS?
The BROWN wire from high-pressure switch HPS to furnace control board is
50.
not making good connection. Repair wire or replace harness.
21
YES NO GO TO
— — INDEX
10 18 —
12 15 —
— — 8
14 13 —
— — 8
— — 8
16 11 —
— — 17
— — 8
19 23
— — 20
— — 21
22 14 —
— — 17
24 29 —
— — 25
— — 26
— — 27
14 28 —
— — 8
— — 30
— — 31
32 33 —
— — 17
34 51 —
36 35 —
— — 8
45 37 —
39 38 —
— — 8
— — 40
42 41 —
— — 8
43 44 —
— — 17
— — 8
— — 46
— — 47
11 48 —
— — 49
14 50 —
— — 8