Mark VIII fan install

[85_SS]

Some Mark VIII fans are 1-speed and some are two speed. On the three speed versions, the wires are as follows:

Blue - Low Speed
Black - Ground
Black/Orange - High Speed


...on the single speed versions there are still three wires, but the centre wire is a dummy and does nothing as there are only the two outer wires connected to the motor. I'm not sure of the wire colours on these versions.

 

[85_SS]

Ok, here's the final schematic and wiring diagram:

 

[BosMobile]

Hey man,thanks.I'll look at mine this weekend to see which one i have.reckon how many amps it draws? thanx again,BO

 

[85_SS]

I borrowed a clamp-on meter from work and at 12V (car off) high speed pulled around 80A in-rush and 21A running. Low speed pulled 52A in-rush and 12.5A running. These values would be a touch higher with the car running.

 

[85_SS]

Due to the unexpected operation of the Hayden controller with the engine off, I have made one final change to the diagram so that the fan will only run with the car on.

What was happening is the fans would run for a minute or two when the car turned off (as expected and designed for). I expected this might happen 2-3 times as the coolant would increase in temp again a few times once the fan stopped. This did happen, but the odd part was after a while the controller would call for the fan to be on for a split second every minute or so and this went on basically until the car naturally cooled down. This wasn't good for the battery and left me with just enough juice to crank the car over a couple times. I didn't like the idea of possibly getting stranded with a dead battery, so I made a minor change that only allows the fan to run with the ignition on:

http://www.motortopia.com/files/cars/al ... bnail1.jpg

http://www.motortopia.com/files/cars/al ... bnail1.jpg

On a side note, regarding how to tell the difference between the 1 and 2 speed Mark VIII fans, I put this quick image together for reference:

 

[BosMobile]

Hey again,yeah i've got the 2-speed!I've been doing other projects,but i'll get around to this one.I'm gonna print this for later reference,i dont know how long these posts stay here.Thanks again,later,BO 8)

 

[McNamee]

I've got a question, I'm having trouble finding a good wire that is hot only on ignition and will work with my fan, I have a rod thermostat that goes into the rad then hooks up to a relay that can switch it on and off based on the temperature and it all works fine but I don't want it running after the car is shut off because it runs for more like 5 minutes. I don't like stabbing all my wires to find out which is good, any suggestions would help. its a stock wiring harness 87 monte ss

 

[85_SS]

I prefer to run a line directly from the fuse panel with a factory connector myself, but if you don't want to do that, lots of people use the choke wire as it will only have power when the engine is running.

 

[McNamee]

thanks 🙂

 

[custom442]

You should have a few options. The hot wire to the dist. should be the easiest to splice (it's pinkish red connecting to dist). This will turn it on at the first/second click when you turn your key. You can also splice the smaller starter wire that gives the car juice on ignition (make sure to use the smaller wire, not the main hot wire on the starter/or solenoid-depending on what starter you have). Or you could use the choke wire as suggested before.