Carrier 58MVP User Manual

Page 14

19.

You have an open wire or bad terminal on either the ORANGE or VIOLET wire between connectors
PL13 and PL3. Repair it or replace blower harness(es).

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20.

Remove tape from door switch and turn power off at main disconnect.

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21.

Does blower wheel rub against blower housing?

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22.

Does blower wheel turn freely?

23.

Is blower wheel firmly mounted on motor shaft?

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24.

Replace entire blower motor or blower control module attached to the blower motor. If you replace
the blower control module go to step 44. Always inspect failed motor for water damage. If present,
find source of water and fix. Check A-coil and/or humidifier.

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25.

Disconnect jumper wire across R and W/W1 thermostat terminals.

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26.

Turn power back on. Depress door switch. Use a piece of tape to hold switch closed. Wait a few
sec for self test before proceeding to next step.

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27.

Do you have 120v between B1 and B2 on furnace control board?

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28.

Do you have 120v between BLACK and WHITE power leads at blower motor MTR2?

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29.

You have an open wire or bad terminal on either the BLACK or WHITE wire between furnace con-
trol board and blower motor MTR2.

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30.

Check blower ON/OFF line. To do this, connect a DC voltmeter across terminals PL3-1 RED (+)
and PL3-5 BLUE (-), then put setup switch SW-6 for COMPONENT TEST in ON position. Does
voltage across RED and BLUE wires change between states as shown below?

• State 1—OFF (-0.1 — 0.1 vdc)
• State 2—ON (9.0 — 10.0 vdc)

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31.

Disconnect PL3 from furnace control board and connect a DC voltmeter across terminals PL3-1 (+)
and PL3-5 (-) on furnace control board, then repeat COMPONENT TEST by turning setup switch
SW-6 OFF and then back ON. Does voltage across PL3-1 and PL3-5 change between states as
shown below?

• State 1—OFF (-0.1 — 0.1 vdc)
• State 2—ON (11.0 — 12.0 vdc)

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32.

Connect a DC voltmeter across RED (+) and BLUE (-) wires at connector PL13 then repeat COM-
PONENT TEST by turning setup switch SW-6 OFF and then back ON. Do you see approximately
the same DC voltages across RED and BLUE wires that you saw in Step 30?

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33.

You have an open wire or bad terminal on either the RED or BLUE wire between connectors PL13
and PL3. Repair it or replace blower harness(es).

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34.

Put setup switch SW-6 for COMPONENT TEST in OFF position.

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35.

Check blower PW line. To do this, connect a DC voltmeter across terminals PL3-1 RED (+) and
PL3-4 YELLOW (-), then put setup switch SW-6 for COMPONENT TEST in ON position. Does volt-
age across the RED and YELLOW wires change between states as shown below?

• State 1—OFF (-0.1 — 0.1 vdc)
• State 2—LOW (2.5 — 3.0 vdc)
• State 3—HIGH (7.0 — 7.5 vdc)

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36.

Disconnect PL3 from furnace control board and connect a DC voltmeter across terminals PL3-1 (+)
and PL3-4 (-) on furnace control board then repeat COMPONENT TEST by turning setup switch
SW-6 OFF and then back ON. Does voltage across PL3-1 and PL3-4 change as shown below?

• State 1—OFF (-0.1 — 0.1 vdc)
• State 2—LOW (3.0 — 4.0 vdc)
• State 3—HIGH (9.0 — 10.0 vdc)

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37.

Connect a DC voltmeter across RED (+) and YELLOW (-) wires at connector PL13 then repeat
COMPONENT TEST by turning setup switch SW-6 OFF and then back ON. Do you see approxi-
mately the same DC voltages across RED and YELLOW wires that you saw in Step 35?

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38.

You have an open wire or bad terminal on either the RED or YELLOW wire between connectors
PL13 and PL3. Repair it or replace blower harness(es).

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39.

Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS. If problem
persists on an intermittent basis, replace blower motor. If problem still persists on an intermittent
basis after replacing blower motor, contact your distributor.

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INDEX

40.

Turn power off and remove blower access panel. Depress door switch. Use a piece of tape to hold
switch closed. Wait a few sec for self test before proceeding to next step.

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41.

Disconnect all thermostat leads from furnace control board. If blower motor is running, wait until it
stops.

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42.

Jumper R and G thermostat terminals. Observe operation of furnace for next 30 sec.

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43.

Approximately 20 sec after energizing G thermostat terminal, does blower motor pause briefly (less
than1/2 sec?)
Note:You can verify this pause using a clamp-on ammeter on BLACK power lead to blower
motor MTR2.

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