Bryant 355MAV Troubleshooting Manual page 28

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
→26.
Remove tape from door switch and turn power off at main disconnect.
→27.
Disconnect PL10 from blower assembly.
→28.
Remove control box assembly from blower shelf and position out of the way.
→29.
Remove blower assembly from furnace.
Disconnect both multi-pin connectors from blower control module attached to the blower motor. Be
→30.
sure to depress release latches on connectors or they may get damaged.
Remove two 1/4-in. hex head bolts from blower control module attached to blower motor. DO NOT
→31.
REMOVE TORX HEAD SCREWS located next to 1/4-in. hex head bolts.
Carefully lift blower control module off blower motor. Depress latch on internal connector to discon-
→32.
nect blower control module from motor portion of blower motor. DO NOT PULL ON WIRES. GRIP
PLUG ONLY.
When blower control module is completely detached from blower motor, verify with standard ohm-
meter 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 resis-
→33.
tance between each combination of pins in motor plug (there are three different combinations, pin
1-2, pin 2-3, and pin 1-3).Resis-tance should be approxi-mately equal across each combination of
pins.
→34.
Did the motor pass the resistance check?
→35.
Does blower wheel turn freely with blower control module removed?
Replace blower control module. Inspect failed blower control module for water damage. If present,
→36.
find source of water and fix. Check A-coil and/or humidifier.
Replace entire blower motor including blower control module. Inspect blower control module for wa-
→37.
ter damage. If present, find source of water and fix. Check A-coil and/or humidifier.
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
Turn power off, remove blower access panel, and disconnect all thermostat leads from furnace con-
1.
trol board.
2. Turn power on and depress door switch. Use a piece of tape to hold switch closed.
3. Jumper R and W/W1 thermostat terminals on furnace control board.
4. Observe operation of furnace for next 8 minutes or until fault occurs.
5. Does fault occur again?
6. Does a different fault occur?
7. Go to page number indicated in Index for fault code flashed.
Go to page number indicated in Index for CLEANUP AND STARTUP
8.
INSTRUCTIONS.
9. Does fault occur within 11 sec after a call for heat?
10. Do you have 120v between I1 and I2 on furnace control board?
11. Do you have 120v between terminals PL7-6 and PL7-12?
You have an open wire or bad terminal on either the BLACK or WHITE wire between furnace con-
12.
trol board and inducer motor MTR1.
13. Are all pins and wire leads intact on connectors between furnace control board and inducer motor?
14. Fix problem.
Turn power off and disconnect jumper wire across R and W/W1 thermostat terminals. Turn power
15.
on and wait a few sec for self test before proceeding to next step.
16. Put setup switch SW-4 for EMER. HEAT in ON position.
17. Jumper R and W/W1 thermostat terminals on furnace control board.
18. Does inducer motor turn on?
19. Does inducer wheel rub against inducer housing?
20. Turn power off.
21. Does inducer wheel turn freely?
22. Replace inducer motor or inducer motor assembly.
23. Replace furnace control board.
Disconnect jumper wire across R and W/W1 thermostat terminals and put setup switch SW-4 for
24.
EMER. HEAT in OFF position.
25. Turn power on and wait a few sec for self test before proceeding to next step.
ACTION
ACTION
—28—
YES NO GO TO
— — 27
— — 28
— — 29
— — 30
— — 31
— — 32
— — 33
— — 34
35 37 —
36 37 —
— — 10
— — 10
YES NO GO TO
— — 2
— — 3
— — 4
— — 5
9 6 —
7 60 —
— — INDEX
— — INDEX
52 35 —
11 14 —
13 12 —
— — 14
15 14 —
— — 8
— — 16
— — 17
— — 18
30 19 —
14 20 —
— — 21
24 22 —
— — 8
— — 8
— — 25
— — 26