2 Radiator fans from one dual speed fan

Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=71462
Printed Date: May 15, 2024 at 2:22 PM

Topic: 2 Radiator fans from one dual speed fan

Posted By: l33t_a2
Subject: 2 Radiator fans from one dual speed fan
Date Posted: January 25, 2006 at 1:21 AM

My car came with a single radiator fan which has two speeds.
It is broken and I am going to replace it with two separate single speed fans.
I want to wire the new ones up so that when the low speed should be on, I have one fan going. When the high speed should be on, I have both going.

I have 3 wires going to the stock fan motor.
Ground, 12v+ for low speed, 12v+ for high speed.

First fan: Ground, 12v from low speed, also 12v from high speed on the same wire.

Second fan: Ground, 12v from high speed. No backflow current from low speed fan.

Is this possible?

The fans are rated at 8 Amps, I could only find a diode rated for 6 amps. I dont even know for sure how diode ratings work. I know how to wire up a basic automotive relay, but thats about the extent of my experience.

The car is a 1990 VW Jetta GLI 16v. It is a daily driver as well as a weekend track car.

Replies:

Posted By: Ween
Date Posted: January 25, 2006 at 1:39 PM

hi,

this should work. bosch type SPDT relay. terminals as follows.

87A to low speed fan wire of vehicle

30 to low/high speed fan (fan 1)

87 & 86 to high speed fan wire and high speed fan (fan 2)

85 to ground and both fans ground leads

hope this helps

mark

Posted By: l33t_a2
Date Posted: January 25, 2006 at 9:31 PM

So youre saying this will work? thats what i got from reading your reply, thanks for the quick response.

Posted By: Ween
Date Posted: January 25, 2006 at 9:37 PM

the diagram drawn is correct except you need a jumper between terminals 87 and 86.

mark

Posted By: l33t_a2
Date Posted: January 25, 2006 at 9:40 PM

ok, and also, if by chance im overthinking this and the low stays positive even when the high goes hot, will that affect the relay setup ?

Posted By: l33t_a2
Date Posted: January 25, 2006 at 9:45 PM

Posted By: geepherder
Date Posted: January 26, 2006 at 2:43 PM

No, it won't hurt anything. That's what you want to happen.

-------------
My ex once told me I have a perfect face for radio.