Signal Too Low
Signal too low
Checking the function of the blower fan
- Ignition on
- Check that the blower fan speed can be controlled using the blower fan selector on the climate control module panel.
Note! Do not select position AUT (ECC); the climate control module controls its own speed at this setting.
- Also check the maximum speed by setting the blower fan selector to the maximum position.
The fault is intermittent if the function is OK.
Is the function OK?
Yes - Intermittent fault
No - Checking the power supply to the blower fan relay
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Checking the power supply to the blower fan relay
Check the power supply to the blower fan relay. Check for the following:
- Defective fuse number 1 (25 A) and fuse number 12 (15 A) in the integrated relay/fusebox in the passenger compartment
- Contact resistance or oxidation in the terminals
- The function of the system relay for the air conditioning (A/C) system, terminal 2
- Open-circuit or short-circuit to ground in the cable between the air conditioning (A/C) system relay and the blower fan relay.
Hint: When the ignition is on, the system relay for the air conditioning (A/C) system must activate. The voltage at blower fan relay terminal #1 should then be approximately battery voltage measured at the ground terminal (0 V).
Remedy as necessary.
Other information:
- To access and replace the system relay for the air conditioning (A/C) system, see Replacing relay in central electrical unit in passenger compartment Replacing Relay In Central Electrical Unit In Passenger Compartment
- To access and replace the blower fan relay, see Replacing the blower fan relay Service and Repair
- For the resistance values, see Electrical / electronic system specifications [1][2]Specifications
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault
- For further information about the circuit, refer to the Wiring diagram Service Manual.
Was a fault detected?
Yes - Verification
No - Checking the connectors, components and wiring
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Intermittent fault
Check the air conditioning (A/C) system relay (terminal 2). Check the blower fan relay connector. Check for contact resistance and oxidation.
Check the cable between the air conditioning (A/C) system relay (position 2) terminal #3 and the blower fan relay terminal #1. Check for an intermittent open-circuit.
Check the signal cable between climate control module terminal #A24 and blower fan relay terminal #3. Check for an intermittent open-circuit. Check for an intermittent short-circuit to ground.
Remedy as necessary.
Other information:
- To remove the climate control module, see Comfort module Removal and Replacement
- To connect the breakout box to the climate control module, see Connecting the breakout box, climate control module Connecting The Breakout Box
- For the voltage of the signal cable, see Climate control signal specifications Signal Specification
- For the resistance values, see Electrical / electronic system specifications [1][2]Specifications
- Checking wiring and terminals. Intermittent faults Checking Wiring and Terminals. Intermittent Faults
Continue - Fault-tracing information
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Fault-tracing information
Information
Fault-tracing information
If the fault is intermittent, do not verify fault-tracing if the fault does not recur.
It is possible to view the information again, or leave fault-tracing for this diagnostic trouble code (DTC).
Do you want to view the information again?
Yes - Attempt New Test
No - FAULT FOUND
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Attempt New Test - Checking the function of the blower fan
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Checking the connectors, components and wiring
- Check the climate control module connector A (30-pin) and the blower fan relay connector. Check for contact resistance and oxidation
- Check the signal cable between climate control module terminal #A24 and blower fan relay terminal #3. Check for a short-circuit to ground. Check for an open-circuit
- Try a new blower fan relay if the wiring and terminals are OK
- Remedy as necessary.
Other information:
- To access and replace the blower fan relay, see Replacing the blower fan relay Service and Repair
- To connect the breakout box, see Connecting the breakout box, climate control module Connecting The Breakout Box
- For the voltage of the signal cable, see Climate control signal specifications Signal Specification
- For the resistance values, see Electrical / electronic system specifications [1][2]Specifications
- Checking wiring and terminals. Permanent fault Checking Wiring and Terminals. Permanent Fault
Continue - Verification
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Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off
- Reinstall the connectors, components etc.
- Ignition on.
Check that the blower fan speed can be controlled using the blower fan selector on the climate control module panel.
Note! Do not select position AUT (ECC); the climate control module controls its own blower fan speed at this setting.
Also check the maximum speed by setting the blower fan selector to the maximum position.
The fault has been remedied if the function is OK.
Is the function OK?
Yes - FAULT FOUND
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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Attempt New Test - Checking the function of the blower fan
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