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2004 saab: The heater fan speed has a mind of its own

Customer Question
I have a 2004 saab...
I have a 2004 saab 93. The heater fan speed has a mind of its own. It runs as fast as it wants to and sometimes runs after the key is taken out of the ignition. This resulted in a flat battery after work yesterday. Was a little [email protected]*ed off to say the least. Any ideas? Thanks in advance.
Mark.... Read full answer
I have a 2004 saab 93. The heater fan speed has a mind of its own. It runs as fast as it wants to and sometimes runs after the key is taken out of the ignition. This resulted in a flat battery after work yesterday. Was a little [email protected]*ed off to say the least. Any ideas? Thanks in advance.
Mark.
Submitted: 9 years ago.Category: Car
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Answered in 1 hour by:
12/11/2009
Auto Mechanic: Randall C, ASE Certified Technician replied 9 years ago
Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 14,203
Experience: 32 years Foreign / Domestic Cars All aspects of Diag and Repair
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Hello, under the dash right alond side of the blower motor is a small computer per say that conrols the fan speeds. When they go bad, the fan may run all the time or not at all or act odd as well. I suspect you need the blower controller. Not hard to replace once you locate the bottom of the blower motor as it is mounted basically right on the bottom of the blower. It is the dark black item in pic below

 

Control Unit, Ventilation Fan, ACC (220b)

Main function
Along with input from the ACC unit, the control unit controls the speed of the ventilation fan motor.

Type
The control unit contains electronics which receive and process the ACC unit's control signal with regards XXXXX XXXXX speed. The control unit grounds the ventilation fan motor and controls fan speed by increasing or decreasing the power supply. Control unit diagnostics occur on the ACC unit input and the outputs to the ventilation fan motor.



Connection
The fan control unit contains two connectors; a four-pin connector connected to the ACC unit and a two-pin connector which is directly-connected to the ventilation fan motor.

Four pin connector.

B+ feed to control unit pin 4 from fuse 23 (fuse board 22) and is connected to ground through pin 1 on grounding point G41.

Fan speed is controlled from ACC unit pin 5 (K32) through control unit pin 3 with a 2 kHz PWM.

Fan control unit pin 2 is connected to ACC unit pin 25 (K32) with a return feed for diagnostics information. The control unit sends a 2 kHz PWM to the corresponding fan speed input. If a fault is detected, the control unit sends the indicated pulse ratio and the ACC unit generates the relevant DTC.

Two-pin connection to the ventilation fan motor.

The control unit is mounted in such a way that its two-pin voltage and ground connector are directly connected to the ventilation fan motor.

The fan motor is connected to ground through the fan control unit on grounding point G41. Fan motor speed is controlled by th

 

graphic

Randall C
Randall C, ASE Certified Technician
Category: Car
Satisfied Customers: 14,203
Experience: 32 years Foreign / Domestic Cars All aspects of Diag and Repair
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Customer reply replied 9 years ago
Cheers XXXXX XXXXX mate. I forgot to mention that it has the standard air con not the climate control. Will It need the same unit?
Auto Mechanic: Randall C, ASE Certified Technician replied 9 years ago

Sorry for delay but stepped away today. The same thing but slightly different location. I should have asked also. the pic below shows location just next to blower motor, dark black item

 

graphic

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