PWM Electric Thermo Fan

When I build the Returnless Fuel Pump controller, I’ll build two so that I can use one for controlling my existing thermatic engine fan. The thermo fan is currently controlled by the MegaSquirt and is simply turned on and off at given temperature set points within the MegaSquirt.

There has been no issue with this approach, but I’d like to regulate the speed of the fan to make it quieter. When on full, it sounds like a buzz saw, mainly because of its cheap fan design and it’s size… small fans are noisier than large fans generally speaking. Megasquirt has 6 Generic PWM’s and 2 Closed loop PWM’s. Below is Generic PWM A setup to modulate the thermo fan based upon coolant temp. Note: the graph is just an estimate at this stage, I’ll have to tune it when it’s all connected up.

The X axis is the coolant temp in degC, the Y axis is the Duty cycle %.

PWM Thermo Fan
Generic PWM A – Thermo Fan Control

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