Checking Blower Fan Control (MCC)
Checking blower fan control (MCC)
Checking blower fan function (MCC)
- Ignition on.
- Activate the blower fan by selecting the blower fan switch positions 1, 2, 3, 4 and 5.
Check if the blower fan starts in all positions.
Did the blower fan start in all positions (at different speeds)?
Yes - Checking cables, blower fan starts
No - Checking cables, blower fan does not start
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Checking cables, blower fan does not start
Check MCC control module, fan resistor and blower fan connector for contact resistance and oxidation according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault. Check that connectors are connected correctly.
Check that the blower fan is not blocked or turning slowly.
Check power supply between MCC control module #A1, #A2, #A3, #A5 and fan resistor terminals 2, 6, 4, 1 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check the power supply between MCC control module #A6 and blower fan for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault and for a short-circuit to ground according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check power supply to MCC control module #A4 for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check ground lead between blower fan and ground terminal for an open-circuit according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
If the cables are OK, try a new blower fan resistor or a new blower fan.
Remedy as necessary.
Other information:
- To access/replace the control module, refer to Replacing ECC control module Removal and Replacement.
- To access/replace the blower fan resistor, refer to Replacing blower fan rheostat (MCC/STANDARD) Removal and Replacement.
- To access/replace the blower fan, refer to Replacing blower fan motor Replacing Blower Fan Motor.
- To connect the breakout box, see Connection of breakout box MCC Connection of Breakout Box MCC.
- For information on signals, refer to Signal descriptions MCC Signal Descriptions MCC.
Continue - Verification
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Checking cables, blower fan starts
Hint: If the blower fan operates but does not change speed when the speed selector is moved this indicates that one or more cables between the MCC control module and the fan resistor are short-circuited to supply voltage.
Check power supply between MCC control module #A1, #A2, #A3, #A5 and the fan resistor terminals 2, 6, 4, 1 for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Check power supply between MCC control module #A6 and the blower fan for a short-circuit to supply voltage according to Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault.
Remedy as necessary.
Other information:
- To access/replace the control module, refer to Replacing or adjusting control cables / mechanical rear section and control panel / front section (Manual climate control / STANDARD) Service and Repair.
- To access/replace the blower fan resistor, refer to Replacing blower fan rheostat (MCC/STANDARD) Removal and Replacement.
- To access/replace the blower fan, refer to Replacing blower fan motor Replacing Blower Fan Motor.
- To connect the breakout box, see Connection of breakout box MCC Connection of Breakout Box MCC.
- For information on signals, refer to Signal descriptions MCC Signal Descriptions MCC.
Continue - Verification
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Verification
Hint: After carrying out the repair check that the fault has been remedied.
- Ignition off.
- Reconnect connectors, reinstall components.
- Ignition on.
- Activate the blower fan by turning blower fan control switch to the different manual speed settings.
Check the blower fan is operating correctly.
Is the fan working?
Yes - Fault has been remedied
No - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit fault-tracing
No - Attempt New Test
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