58SU0A (Series 2 & 3): Troubleshooting Guide
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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Status Code 42 - Inducer Motor Fault
Indicates RPM pulses from inducer are not detected within 20 seconds after a heat request, that inducer RPM was lost for greater than 5 seconds during
operation, or that inducer is operating outside of its valid speed range
STEP ACTION YES NO GO TO
1.
Shut the power off, remove the blower access panel and disconnect the R thermostat lead from the
furnace control board
2
2. Turn the power on and depress the door switch. Use a piece of tape to hold it closed. 3
3. Jumper the R and W thermostat terminals. 4
4. Observe the operation of the furnace for the next 10 minutes or until fault occurs. 5
5. Does status code 42 flash? 9 6
6. Does a different status code flash? 7 8
7. Go to page number indicated in the Index for the section covering the status code. INDEX
8. Go to page number Indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. INDEX
9. Does the inducer motor turn on? 27 10
10. Hook an AC voltmeter across PL2-2 and L2 on the furnace control. Is 115-VAC across PL2-2 and L2? 12 11
11. Replace the furnace control. 15
12. Do you have 115-VAC across PL13-4 and PL13-5? 14 13
13.
You have an open wire or bad terminal on either the BLACK or WHITE wire between the furnace control
and the inducer motor. Repair or replace main wire harness.
15
14. Are all pins and wire leads intact on connectors between the furnace control and the inducer motor? 16 15
15. Fix Problem 8
16. Turn power off and disconnect jumper wire across R and W thermostat terminals 17
17. Turn power ON 18
18.
Check the inducer PWM line. To do this connect a DC voltmeter across terminals PL13-1 GRAY (+) and
PL13-2 YELLOW (-).
Note: The terminals can be damaged if the voltmeter probe is jammed into the connector. Use caution
when checking.
Run COMPONENT TEST by briefly shorting the TEST/TWIN terminal to the C terminal at the thermostat
terminal strip. Does the voltage across PL13-1 and PL13-2 change states as shown below?
- State 1 - OFF (0 - 4.0 VDC)
- State 2 - MED (6.0 - 9.0 VDC)
23 19
19. Turn Power OFF 20
20. Do you have continuity between PL13-1 and PL1-11 21 22
21. Do you have continuity between PL13-2 and PL1-9 11 22
22.
You have an open wire or bad terminal on either the BROWN or YELLOW wire between the furnace
control and the inducer motor. Repair or replace the wire harness
15
23. Does inducer wheel turn freely? 26 24
24. Does the inducer cooling fan rub against the inducer housing? 15 25
25. Does the inducer wheel rub against the inducer housing? 15 26
26. Replace the inducer assembly 15
27. Does status code 42 flash within 20 seconds after a call for heat? 28 48
28. Turn power off and disconnect jumper wire across R and W thermostat terminals 29
29. Unplug transducer harness at connection PL12 30
30. Turn power on and Jumper the R and W thermostat terminals 31
31. Does status code 42 flash within 20 seconds after a call for heat? 33 32
32. Does status code 31 flash 40 11
33. Turn power off and disconnect jumper wire across R and W thermostat terminals. 34
34. Reconnect the transducer connection PL12 35
35. Turn Power ON 36
36.
Check the RPM feedback line. To do this, connect a DC voltmeter across terminals PL13-1 Gray (+) and
PL13-3 ORANGE (-). Run COMPONENT TEST by briefly shorting the TEST/TWIN terminal to the C
terminal at the thermostat terminal strip. Does the voltage across PL13-1 and PL13-3 change states as
shown below?
- State 1 – OFF (15 – 16 VDC)
- State 2 – MED (13 – 14.5 VDC)
NOTE: Values listed are general guidelines and measured values may differ from those listed. Monitor for
the voltage change between the OFF and ON operational states
37 26
37. Turn power OFF 38
38. Do you have continuity between PL13-3 and PL1-7? 11 39
39.
You have an open wire or bad terminal on the ORANGE wire between PL13 and PL1. Repair or replace
harness
15
40. Turn off power and reconnect the transducer connection at PL12 41
41.
Connect 1 side of a slope manometer with a tee to the collector box pressure tap. Refer to pressure check
connection illustration in APPENDIX C: Transducer Operational Check
42
42.
Check for proper output of the transducer. To do this, connect a DC voltmeter across terminals PL12-2
GREEN and PL12-3 BLACK (+).
43
43.
Turn power ON and run COMPONENT TEST by briefly shorting the TEST/TWIN terminal to the C terminal
at the thermostat terminal strip.
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