Carrier 58MVP - Manual (Page 9)

IMPROPER OPERATION WITH NO FLASHING FAULT CODE—Generally, this indicates there is no power to
furnace control board.
STEP ACTION YES NO GO TO
1. Make sure power is on. — — 2
2.
Remove blower access panel and depress door switch. Use a piece of tape to hold switch closed.
Wait a few sec for self test before proceeding to next step.
— — 3
3. Make sure thermostat is calling for heat. — — 4
4. Make sure thermostat fan control is in AUTO position if equipped. — — 5
5. Check fuses, breakers, or manual disconnects to be sure they are correctly set. — — 6
6. Does 120-v wiring match unit wiring schematic? 9 7 —
7. Fix problem. — — 8
8. Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. — — INDEX
9. Do you have 120 vac at primary leads P1 and P2 on furnace control board? 14 10 —
10. Do you have 120 vac to furnace control board? 11 12 —
11. Check all 120-vac connections at furnace control board. If necessary, replace furnace control board. — — 8
12. Turn power off. — — 13
13. Check continuity of power supply leads and door switch if wired with 120 vac. — — 7
14. Do you have 24v between SEC-1 and SEC-2 on furnace control board? 19 15 —
15. Turn power off. — — 16
16. Do you have continuity across door switch? 17 18 —
17. Replace transformer. If transformer fails again, replace transformer and furnace control board. — — 8
18. Replace door switch. — — 8
19. Do you have 24v between R and Com on furnace control board? 21 20 —
20. Replace furnace control board. — — 8
21. Do you have 24v between W/W1 and Com on furnace control board? 24 22 —
22. Check to see that thermostat is calling for heat. — — 23
23. You have a defective thermostat or a break in the wiring between thermostat and furnace. — — 7
24. Does furnace respond to the call for heat? 27 25 —
25. Turn power off. — — 26
26.
Press down on microprocessor chip and make sure it is properly seated to furnace control board. If
it is, replace furnace control board.
— — 7
27.
Does furnace keep repeating the following cycle? Inducer motor MTR1 runs, inducer motor MTR1
stops, furnace control board goes through a self-test sequence, blower motor runs for 1 minute, and
then cycle repeats.
28 34 —
28. Disconnect BROWN wire to gas valve GV. — — 29
29.
Does furnace still alternately cycle inducer motor, go through a self test, and then run blower motor
as described in Step 27?
30 37 —
30. Disconnect humidifier lead from HUM terminal on furnace control board. — — 31
31.
Does furnace still alternately cycle inducer motor, go through a self test, and then run blower motor
as described in Step 27?
33 32 —
32. There is a direct short in wiring to humidifier solenoid coil, or short is inside humidifier solenoid coil. — — 7
33.
There is a direct short in either the pressure switch circuits, gas valve GV, or wiring to gas valve
GV. If hot surface ignitor comes on during the cycle, short is in gas valve or wiring to gas valve.
— — 7
34.
Does furnace ever abruptly shut down with no fault code, no inducer post purge, no blower off de-
lay, and then restart heating cycle?
35 38 —
35. Disconnect BROWN wire to gas valve GV. — — 36
36.
Does furnace still abruptly shut down with no fault code, no inducer post purge, no blower off delay,
and then restart heating cycle?
39 37 —
37. Replace gas valve. — — 8
38.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. If problem
persists on an intermittent basis, replace furnace control board. If problem still persists after replac-
ing furnace control board, contact your distributor.
— — INDEX
39. Disconnect humidifier lead from HUM terminal on furnace control board. — — 40
40.
Does furnace still abruptly shut down with no fault code, no inducer post purge, no blower off delay,
and then restart heating cycle?
33 32 —
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