# Carrier Infinity 69 Trouble Code 42



## bodya1 (Dec 5, 2010)

Has anyone experience the trouble? How did you resolve?


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## hvactech126 (Nov 11, 2010)

does the inducer motor run at all? if so, check drain hose for blockage and or trap. If not then have pro check it out because it is Variable speed

Fault Code 42
INDUCER OUTSIDE VALID SPEED RANGE—This 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 control
board. — — 2
2. Turn power on and depress door switch. Use a piece of tape to hold switch closed. — — 3
3. Jumper R and W/W1 thermostat terminals on furnace control board. — — 4
4. Observe operation of furnace for next 8 minutes or until fault occurs. — — 5
5. Does fault occur again? 9 6 —
6. Does a different fault occur? 7 60 —
7. Go to page number indicated in Index for fault code flashed. — — INDEX
8. Go to page number indicated in Index for CLEANUP AND STARTUP INSTRUCTIONS. — — INDEX
9. Does fault occur within 11 sec after a call for heat? 52 35 —
10. Do you have 120v between I1 and I2 on furnace control board? 11 14 —
11. Do you have 120v between terminals PL7-6 and PL7-12? 13 12 —
12. You have an open wire or bad terminal on either the BLACK or WHITE wire between furnace control
board and inducer motor MTR1. — — 14
13. Are all pins and wire leads intact on connectors between furnace control board and inducer motor? 15 14 —
14. Fix problem. — — 8
15. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. Turn power
on and wait a few sec for self test before proceeding to next step. — — 16
16. Put setup switch SW-4 for EMER. HEAT in ON position. — — 17
17. Jumper R and W/W1 thermostat terminals on furnace control board. — — 18
18. Does inducer motor turn on? 30 19 —
19. Does inducer wheel rub against inducer housing? 14 20 —
20. Turn power off. — — 21
21. Does inducer wheel turn freely? 24 22 —
22. Replace inducer motor or inducer motor assembly. — — 8
23. Replace furnace control board. — — 8
24. Disconnect jumper wire across R and W/W1 thermostat terminals and put setup switch SW-4 for
EMER. HEAT in OFF position. — — 25
25. Turn power on and wait a few sec for self test before proceeding to next step. — — 26
26. Check 12-vdc line. To do this, connect a DC voltmeter across terminals PL1-6 BROWN (+) and
PL1-7 GREEN (-). Is voltage across BROWN and GREEN wires 11.5 — 12.5 vdc? 27 23 —
27. Turn power off. — — 28
28. Do you have continuity between PL7-2 and PL1-6? 22 29 —
29. You have an open wire or bad terminal on BROWN wire between connectors PL7 and PL1. — — 14
30. Disconnect jumper wire across R and W/W1 thermostat terminals and put setup switch SW-4 for
EMER. HEAT in OFF position. — — 31
31.
Check RPM feedback line. To do this, connect a DC voltmeter across terminals PL1-6 BROWN (+)
and PL1-5 ORANGE (-), then put setup switch SW-6 for COMPONENT TEST in ON position. Does
voltage across BROWN and ORANGE wires change between states as shown below?
• State 1—OFF (11.5 — 12.5 vdc)
• State 2—LOW (10.2 — 11.2 vdc)
• State 3—HIGH (8.4 — 9.4 vdc)
23 32 —
32. Turn power off. — — 33
33. Do you have continuity between PL7-1 and PL1-5? 22 34 —
34. You have an open wire or bad terminal on ORANGE wire between connectors PL7 and PL1. — — 14
35.
Does fault occur a few sec after low-pressure switch LPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on low-pressure switch LPS
and Com on furnace control board to know when low-pressure switch LPS makes.
36 48 —
36. Is inducer motor rotating in direction shown on inducer housing? 37 22 —
37. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. — — 38
38. Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side
with a tee to gas valve air pressure fitting. Refer to pressure check diagram in Appendix C. — — 39
39. Turn power on and wait several sec, then jumper R and W/W1 thermostat leads on furnace control
board. — — 40
40.
Do you have more than 1.0 in. wc pressure drop (0.80 in. wc on trophy unit) across heat exchangers
when low-pressure switch LPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on low-pressure switch LPS
and Com on furnace control board to know when low-pressure switch LPS makes.
47 41 —
41. Turn power off. — — 42
42. Is inducer blower wheel okay? 44 43 —
29
43. If possible, replace inducer wheel. Otherwise, replace inducer motor assembly. — — 8
44. Is there any frost build-up on combustion-air inlet? 45 46 —
45. The problem is caused by reversed vent and combustion-air pipes or some other moist air entering
combustion-air pipe. — — 14
®46.
You have inadequate combustion-air supply. This may be caused by:
- Excessive restriction in combustion-air or vent pipe.
- Internal restriction in coupling box or secondary heat exchangers
— — 14
®47. Replace pressure switch assembly. — — 70
®48. Is unit a trophy unit? 50 49 —
®49. Does fault occur before blower motor turns ON? 47 51 —
®50.
Replace pressure switch assembly with pressure switch assembly used in NON-trophy models or
replace furnace control board. If you replace furnace control board make sure replacement control
has a date code of 9837 or later. Only replace the pressure switch assembly or the furnace control
board NOT both.
— — 70
®51. Replace furnace control board. — — 70
52. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. — — 53
53. Turn power on and wait several sec before proceeding to next step. — — 54
54. Disconnect collector box tube to pressure switch assembly. — — 55
55. Jumper R and W/W1 thermostat terminals on furnace control board. — — 56
56. Does Fault Code 42 occur within 11 sec after a call for heat? 57 58 —
57. Reconnect collector box tube to pressure switch assembly. — — 10
58. Reconnect collector box tube to pressure switch assembly. — — 36
59. Go to page number indicated in Index for CLEANUP AND STARTUP INSTRUCTIONS. If problem
persists on an intermittent basis, contact your distributor. — — INDEX
60. Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. — — 61
61. Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat terminals on furnace
control board. — — 62
62.
Does fault occur a few sec after high-pressure switch HPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on high-pressure switch
HPS and Com on furnace control board to know when high-pressure switch HPS makes.
63 67 —
63. Turn power off and disconnect jumper wire across R, W/W1, and W2 thermostat terminals. — — 64
64. Connect 1 side of a slope manometer with a tee to collector box pressure tap. Connect other side
with a tee to gas valve air pressure fitting. Refer to pressure check diagram in Appendix C. — — 65
65. Turn power on and wait several sec, then jumper R, W/W1, and W2 thermostat terminals on furnace
control board. — — 66
66.
Do you have more than 1.9 in. wc pressure drop across heat exchangers when high-pressure
switch HPS makes?
NOTE: Check for 24v between the N.O. (Normally Open) contact on high-pressure switch
HPS and Com on furnace control board to know when high-pressure switch HPS makes.
47 44 —
®67. Does fault occur a few sec after main burners ignite? 63 68 —
®68. Observe operation of furnace in high heat for next 8 minutes or until fault occurs. — — 69
®69. Does the fault occur? 22 59 —
®70. If problem still persists check for internal restriction in coupling box or secondary heat exchangers. — — 14


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## Marty S. (Oct 31, 2009)

Holy cow tech. That's the most detailed trouble shooting post I've ever seen on here. Great job! :thumbsup:


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## yuri (Nov 29, 2008)

And he typed it by hand (not copy and pasting):yes::thumbup:


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## hvactech126 (Nov 11, 2010)

:thumbup:nope, not copying an pasting at all!!!!

I just happened to have that install manual already downloaded to my computer...............


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