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