The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - Trinary and 3 relay electric fan questions

Accelo · 07-01-2022, 08:43 PM

The set up that came with my radiator had a system that ran one fan at full speed at the lower cut in from the ECM and started the other fan at the high temperature cut in from the ECM/ECU. (The first fan continues to run with the second fan on). It was my preference to have the quieter low speed on both fan option. It is way more complicated and in general I would not recommend it because of the wiring complications it introduces.

My fans were not advertised as two speed. Just running them in series cuts the voltage and thus the speed of both fans. It also requires another relay (three instead of two).
I would rate this as not typically worth the hassles as the motor will stay just a cool either way.

07-01-2022, 08:43 PM	#11
Accelo Registered User Join Date: Mar 2015 Location: washington Posts: 2,162	Re: Trinary and 3 relay electric fan questions The set up that came with my radiator had a system that ran one fan at full speed at the lower cut in from the ECM and started the other fan at the high temperature cut in from the ECM/ECU. (The first fan continues to run with the second fan on). It was my preference to have the quieter low speed on both fan option. It is way more complicated and in general I would not recommend it because of the wiring complications it introduces. My fans were not advertised as two speed. Just running them in series cuts the voltage and thus the speed of both fans. It also requires another relay (three instead of two). I would rate this as not typically worth the hassles as the motor will stay just a cool either way.