Fault Code 42
INDUCER OUTSIDE VALID SPEED RANGEÐThis fault indicates that inducer motor is not operating at calculated RPM or has not started within 10 sec after a call for heat.
STEP | ACTION | YES | NO | GO TO | |
1. | Turn power off, remove blower access panel, and disconnect all thermostat leads from furnace con- | Ð | Ð | 2 | |
trol board. | |||||
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2. | Turn power on and depress door switch. Use a piece of tape to hold switch closed. | Ð | Ð | 3 | |
3. | Jumper R and W/W1 thermostat terminals on furnace control board. | Ð | Ð | 4 | |
4. | Observe operation of furnace for next 8 minutes or until fault occurs. | Ð | Ð | 5 | |
5. | Does fault occur again? | 9 | 6 | Ð | |
6. | Does a different fault occur? | 7 | 60 | Ð | |
7. | Go to page number indicated in Index for fault code flashed. | Ð | Ð | INDEX | |
8. | Go to page number indicated in Index for CLEANUP AND STARTUP INSTRUCTIONS. | Ð | Ð | INDEX | |
9. | Does fault occur within 11 sec after a call for heat? | 52 | 35 | Ð | |
10. | Do you have 120v between I1 and I2 on furnace control board? | 11 | 14 | Ð | |
11. | Do you have 120v between terminals | 13 | 12 | Ð | |
12. | You have an open wire or bad terminal on either the BLACK or WHITE wire between furnace con- | Ð | Ð | 14 | |
trol board and inducer motor MTR1. | |||||
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13. | Are all pins and wire leads intact on connectors between furnace control board and inducer motor? | 15 | 14 | Ð | |
14. | Fix problem. | Ð | Ð | 8 | |
15. | Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. Turn power | Ð | Ð | 16 | |
on and wait a few sec for self test before proceeding to next step. | |||||
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16. | Put setup switch | Ð | Ð | 17 | |
17. | Jumper R and W/W1 thermostat terminals on furnace control board. | Ð | Ð | 18 | |
18. | Does inducer motor turn on? | 30 | 19 | Ð | |
19. | Does inducer wheel rub against inducer housing? | 14 | 20 | Ð | |
20. | Turn power off. | Ð | Ð | 21 | |
21. | Does inducer wheel turn freely? | 24 | 22 | Ð | |
22. | Replace inducer motor or inducer motor assembly. | Ð | Ð | 8 | |
23. | Replace furnace control board. | Ð | Ð | 8 | |
24. | Disconnect jumper wire across R and W/W1 thermostat terminals and put setup switch | Ð | Ð | 25 | |
EMER. HEAT in OFF position. | |||||
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25. | Turn power on and wait a few sec for self test before proceeding to next step. | Ð | Ð | 26 | |
26. | Check | 27 | 23 | Ð | |
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27. | Turn power off. | Ð | Ð | 28 | |
28. | Do you have continuity between | 22 | 29 | Ð | |
29. | You have an open wire or bad terminal on BROWN wire between connectors PL7 and PL1. | Ð | Ð | 14 | |
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30. | Disconnect jumper wire across R and W/W1 thermostat terminals and put setup switch | Ð | Ð | 31 | |
EMER. HEAT in OFF position. | |||||
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| Check RPM feedback line. To do this, connect a DC voltmeter across terminals |
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31. | voltage across BROWN and ORANGE wires change between states as shown below? | 23 | 32 | Ð | |
· State 1ÐOFF (11.5 Ð 12.5 vdc) | |||||
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| · State 2ÐLOW (10.2 Ð 11.2 vdc) |
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| · State 3ÐHIGH (8.4 Ð 9.4 vdc) |
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32. | Turn power off. | Ð | Ð | 33 | |
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33. | Do you have continuity between | 22 | 34 | Ð | |
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34. | You have an open wire or bad terminal on ORANGE wire between connectors PL7 and PL1. | Ð | Ð | 14 | |
| Does fault occur a few sec after |
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35. | NOTE: Check for 24v between the N.O. (Normally Open) contact on | 36 | 48 | Ð | |
| and Com on furnace control board to know when |
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36. | Is inducer motor rotating in direction shown on inducer housing? | 37 | 22 | Ð | |
37. | Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. | Ð | Ð | 38 | |
38. | Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side | Ð | Ð | 39 | |
with a tee to gas valve air pressure fitting. Refer to pressure check diagram in Appendix C. | |||||
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39. | Turn power on and wait several sec, then jumper R and W/W1 thermostat leads on furnace control | Ð | Ð | 40 | |
board. | |||||
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| Do you have more than 1.0 in. wc pressure drop (0.80 in. wc on trophy unit) across heat exchang- |
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40. | ers when | 47 | 41 | Ð | |
NOTE: Check for 24v between the N.O. (Normally Open) contact on | |||||
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| and Com on furnace control board to know when |
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41. | Turn power off. | Ð | Ð | 42 | |
42. | Is inducer blower wheel okay? | 44 | 43 | Ð |
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