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PWM driver for fan or fuel pump

The cooling fan and fuel pump draws a lot of power. An external power driver is required to control such a big load.

Warning

One driver, one fan. If you need to connect two fans, you will need two drivers.

Stock fan with PWM control

Some cars has fans with integrated PWM controller

BMW E46 fan

Older version: - Frequency 50 Hz - Duty 10 - 90%

Newer version: - Frequency 100 Hz - Duty 10 - 95%

Stock driver

There are several inexpensive stock fan drivers.

Toyota

Mitsubishi / Mazda 1355A124

DIY driver

The circuit must be mounted in a metal case to provide heat dissipation. Mount the diode and transistor onto the case using insulators and thermal grease. We recommend the AOS220 ceramic insulator.

Take 12V power directly from the battery through a powerful fuse. Choose your fuse carefully. Cheap fuses melt easily under load. Power wires must be of sufficient size.

Warning

Resistor R2 must be connected near the ECU. If suddenly you want to transfer the resistor to the driver case, then with the ignition off, the fan will turn on

PWM setting

Example for configuring a PWM output for fan control:

  • PWM output X4
  • Engine T control
  • when reaching 87deg, the fan will turn on at 40% power
  • the power will increase with increasing temperature, and when 98deg is reached, the fan will operate at 100% power