electric cooling fans

[Joyridin]

Pulse Width Modulation. GM uses it on their electric fans and fuel pumps.

Instead of the fans coming on full blast and a specified temperature, then shutting off causing a huge load to be dumped on your alternator, you set the temperature down a bit lower and as the vehicle gets warmer, the fans slowly come on. If/when it hits your maximum temperature, the fans will be running at full speed. Most of the time though, that doesn't really happen because the fans have been running at half speed keeping the temperature in check.

GM has used this on their fuel pumps since around 2015, maybe a bit earlier. Since the fuel pumps are being modulated constantly, there is not need for a return line. When the car needs more fuel, they speed up the pumps. When you are idling, the pumps run slow. It saves the pumps and again, reduces the need for huge alternators that are capable to handle the huge load dumped on them.

Here is the fan unit I used. I have the HF-125 for my twin Derale fans. Supposedly the Derale PMW unit is not too good.
https://www.autocoolguy.com/home

I heard a few people use this one also. I have never used it. It is available at several places.
https://www.northernradiator.com/HIG...S?pageSize=200