Saab 900 II - Speed control for heating-system fan | HELLA

In the above vehicles, a defective fan control unit can result in the passenger compartment fan operating only at the highest speed.

If the fan speed can no longer be controlled by the control unit or the fan operates only at the highest setting, the cause is probably a defect in the electronic fan control unit. In most cases, the transistor (MOSFET) on the circuit board has failed.

To access the fan control unit, the glove compartment must first be removed. If the left trim panel in the front passenger foot space is also removed, then there is free access to the control unit. Then the control unit can be replaced.

Somewhat skilled technicians could also repair the control unit by replacing the transistor.

For this procedure, the following accessories/replacement parts are needed:

• Transistor (Type IRFP064N), see drawing
• Soldering iron, ca. 30W
• Desoldering pump
• Solder
• Thermal grease
• Screwdriver, narrow
• Blade
• Harness tape, temperature-resistant