Status Code 42 - Inducer Motor Fault - Carrier PG9UAA Troubleshooting Manual

STEP
29. Does the voltage fluctuate as described in step 28?
30. Reconnect PL3 to the variable speed furnace control and connect a DC voltmeter across
terminals PL3- -4 BLUE (+) and PL3- -2 GREEN (- -). Does the voltage fluctuate as de-
scribed in step 28?
31. Disconnect PL13 from the blower motor and connect a DC voltmeter across the BLUE (+)
and GREEN (- -) wires at connector PL13. Does the voltage fluctuate as described in step
28?
32. You have an open wire or bad terminal on the BLUE wire between connectors PL3 and
PL13. Repair it or replace harness.
33. Disconnect PL13 from the blower motor and connect a DC voltmeter across the BLUE (+)
and GREEN (- -) wires at connector PL13. Does the voltage fluctuate as described in step
28?
34. You have short to ground on the BLUE wire between connectors PL3 and PL13. Repair it
or replace harness.
35. The blower motor and furnace control are communicating but the RPM must be below
250.
WARNING: Wait at least 5 minutes after disconnecting line voltage from equipment before opening blower motor to prevent
electric shock which can cause personal injury or death.
STEP
36. Remove tape from door switch and turn power off at main disconnect.
37. Disconnect both multi- -pin connectors from blower control module attached to the blower
motor. Be sure to depress release latches on connectors or they may get damaged.
38. Remove control box assembly from blower shelf and position out of the way.
39. Remove blower assembly from furnace.
Remove two phillips head or two ¼- -in. hex head bolts from blower control module at-
40.
tached to blower motor.
41. Carefully lift blower control module off blower motor. Depress latch on internal connector
to disconnect blower control module from motor portion of blower motor. DO NOT
PULL ON WIRES. GRIP PLUG ONLY.
42. When blower control module is completely detached from blower motor, verify with stand-
ard ohmmeter that the resistance from each motor lead in motor plug to unpainted motor
end plate is greater than 100k ohms. Then verify motor windings are not shorted or open
by measuring resistance between each combination of pins in motor plug (there are three
different combinations, pin 1- -2, pin 2- -3, and pin 1- -3). Resistance should be approxim-
ately equal across each combination of pins.
43. Did the motor pass the resistance check?
44. Does blower wheel turn freely with blower control module removed?
45. Replace blower control module. Inspect failed blower control module for water damage. If
present, find source of water and fix. Check A- -coil and/or humidifier.
46. Replace entire blower motor including blower control module. Inspect blower control
module for water damage. If present, find source of water and fix. Check A- -coil and/or
humidifier.
Status Code 42
INDUCER MOTOR FAULT - - This status code indicates the inducer has not started within 20 seconds after a call for
heat, the inducer RPM is outside its valid range of operation, or the inducer RPM signal was lost for 5 seconds during
operation.
STEP
1. Shut the power off, remove the blower access panel and disconnect the R thermostat lead
from the furnace control board.
2. Turn the power on and depress the door switch. Use a piece of tape to hold it closed.
3. Jumper the R and W/W1 thermostat terminals.
4. Observe the operation of the furnace for the next 8 minutes or until fault occurs.
5. Does status code 42 flash?
6. Does a different status code flash?
7. Go to page number indicated in the Index for the section covering the status code.
8. Go to page number Indicated in Index for CLEANUP AND START- -UP INSTRUC-
TIONS.
9. Does the inducer motor turn on?
ACTION
ACTION
ACTION
27
YES NO GO TO
30 20
31 33
15 32
15 34
14
YES NO GO TO
37
38
39
40
41
42
43
44 46
45 46
YES NO GO TO
9 6
7 54
INDEX
INDEX
27 10
8
8
8
8
2
3
4
5