Carrier 58MVP Troubleshooting Manual page 22

Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side
25.
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 terminals on furnace con-
26.
trol board.
27. Monitor slope manometer. Does pressure reading appear to be stable when fault occurs?
28. Check for a sag in vent pipe. If problem persists, replace inducer motor.
29. Disconnect jumper wire across R and W/W1 thermostat terminals and wait until blower stops.
30. Jumper R, W/W1, and W2 thermostat terminals on furnace control board.
31. Does high-pressure switch HPS make, then break several times at start of cycle 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 on furnace control
34.
board?
The YELLOW wire to high-pressure switch HPS is not making good connection. Repair or replace
35.
it.
Do you have at least 1.90 in. wc pressure drop across heat exchangers when fault occurs? Deter-
mine this by connecting 1 side of slope manometer with a tee to collector box pressure tap. Con-
36.
nect other side with a tee to gas valve air pressure fitting. Refer to pressure check diagram in Ap-
pendix 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 other moist air entering
43.
combustion-air pipe.
44. You have excessive restriction in combustion-air or vent pipe.
45. Turn power off and disconnect jumper wire across R, W/W1, and W2 thermostat terminals.
Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat terminals on fur-
46.
nace control board.
Do you have 24v between connector terminal PL2-4 and Com on furnace control board when fault
47.
occurs?
48. Turn power off.
Do you have continuity across terminal PL2-4 and N.O. (Normally Open) contact on high-pressure
49.
switch HPS?
The BROWN wire from high-pressure switch HPS to furnace control board is not making good con-
50.
nection. Repair wire or replace harness.
51. Turn power off and disconnect jumper wire across R, W/W1, and W2 thermostat terminals.
Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side
52.
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, W/W1, and W2 thermostat terminals on fur-
53.
nace control board.
54. Monitor slope manometer. Does pressure reading appear to be stable when fault occurs?
Replace pressure switch assembly. If problem persists, check wiring for an intermittent connection
55.
in high-pressure switch HPS circuit.
56. Check for a sag in vent pipe. If problem persists, replace inducer motor.
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