Cheap Mark 8 Fan Controller October 26, 2011, 12:40:54 AM I've been kicking around an idea that I'd like to share with you guys. I've been working on a way to control a Mark 8 fan reliably without a lot of cash outlay. Just about anyone who peruses Ford, performance-related forums like this one knows about the ability of Mark 8 fans to cool an engine. It's also a well known fact that Mark 8 fans draw a butt load of amps at start-up (roughly 80 amps). The reason why most electric fan controllers out there can't reliably control Mark 8 fans, is because of the massive amount of amps they draw. The only 2 commonly used options I know of being used to control these fans, is to thermostatically control the fan with an expensive controller (which will cost you about $200), or to maunually control it with a toggle swith and relay.I think I've figured out a way to thermostatically control one of these fans reliably, while spending very little money in the process. The only parts you'd need to do what I'm proposing, would be a $50 Hayden 2 Speed Electric Fan Controller and 2 continuous duty, 12 volt solenoids ($25).Obviously, Mark 8 fans have a low speed circuit and a high speed circuit. The low speed circuit is good for cruising around when your A/C is off. When you ARE running your A/C however, the high speed option is your best bet.If you installed one of those Hayden 2 Speed Controllers and used a continuous duty solenoid to handle the amperage of the low speed fan circuit and another solenoid to handle the amps of the high speed circuit, you'd have a cheap, reliable way of controlling the fan. So what do you think about doing it this way? The only component that you should have to ever replace in this set up would be the solenoids, if they failed. The Hayden Controller should last a really long time, because it's not being exposed to any more amperage than it takes to energize the solenoids. And only one solenoid will ever be energized at a time on top of that.So... Am I certifiably crazy, or what? :) Quote Selected
Cheap Mark 8 Fan Controller Reply #1 – October 27, 2011, 10:53:02 AM I used two relays that were wired up so that the AC triggered one and the manual switch in the car triggered the other one. If the manual switch was on then the AC relay had no power and did not need any because the manual switch had the fan running anyhow. This setup did not take advantage of the low speed function of the fan but it worked pretty good for a couple of years. The only thing it did was prematurely wear out the contacts in the relay due to the end rush of the fan motor being so high when it was first started. This eventually wore the brushes on the motor out a lot quicker as well. I found out later on that a diode is needed between the negative and positive terminals of the fan. This allows the load to be dissipated off the fan motor when the switch or AC relay is turned off.Anyhow, I think your idea will work but just remember that you will need a pair of 80A relays and a diode.I opted for the DC Controls module for both of my Mark VIII fans as it ramps the speed of the fan up and down like a variable speed controller and also has what I would call a soft start function which easier on the fan when it first starts and it also reduces the amperage required to start the fan.Darren Quote Selected
Cheap Mark 8 Fan Controller Reply #3 – October 27, 2011, 01:22:50 PM Tom....where do you source those fans? Quote Selected
Cheap Mark 8 Fan Controller Reply #4 – October 27, 2011, 03:16:27 PM Looks like these, but these are pushers...top lefthttp://www.omega-usa.com/client/images/bus%20cond%20fan%20flyer.pdf Quote Selected
Cheap Mark 8 Fan Controller Reply #5 – October 27, 2011, 04:49:55 PM One other note, by the time you mess with installing a the whole relay setup it is seriously easier to wire up the DC Controller and be done with it. I was never happy with the on/off functionality of the fan with just the relays.To clarify, the switch in the car supplied 12V+ to the coil of the Bosch relay. In my case 12V+ was on 86, ground went to 85, 12V+ from the battery went to 30, and the 12V+ to the fan came from 87. This was the manual on/off side of the setup. The AC relay was wired basically the same way but the 12V+ trigger came from the constant hot side of the AC clutch cycle switch mounted on the A/C Acspoogeulator/Receiver Drier. If you pull the 12V+ trigger from between the clutch cycle switch and the AC compressor the fan will cycle with the clutch. Again, I grabbed the trigger under the hood as it was easier than pulling the radio and finding the wire under the dash and then running the wire out to the engine bay. I wired the AC relay as follows: 12V+ trigger from AC clutch cycle switch on 86, ground on 85, 12V+ to the fan from 87. The only difference was to run a wire from the manual relay off of 87a over to 87 on the AC relay. To figure that one out a person needs to know that 87 and 87a are common until the coil of the relay is energized then 87 and 30 are common. This kept the two circuits from back feeding one another. I think Tom's idea of putting the diode in line so that the AC or manual switch can control a single relay is brilliant in lieu of running two relays.Complicating a simple circuit is all in the eye of the beholder. Its all what a person wants to do and there are different ways to do it. I wanted two relays so if one failed I could get home but that was just my thinking at that point in time. Now, you could not talk me out of the DC Controller on either car.Darren Quote Selected
Cheap Mark 8 Fan Controller Reply #9 – October 28, 2011, 11:04:55 AM I know you can do that in theory, but wondered if there is something different because some are listed as not reversible. Quote Selected
Cheap Mark 8 Fan Controller Reply #10 – October 28, 2011, 12:49:41 PM Tom,With the DC Controller it is like a variable frequency drive. You hook it up to the high speed on the fan and it will ramp the fan up and down per the temperature props input. It also has inputs for the AC, the ability to have it continue to run and cool the motor down after the car is shut off, a selector for under drive pullies, and it starts the fan like a soft starter rather than an across the line started which is what the relays do. The soft start feature is easier on the Siemens motor the fan uses and they last longer. All of that and the controller is super easy to install. I have some pictures of the install on my Bird here:http://www.foxtbirdcougarforums.com/showthread.php?31690-Mark-VIII-Electric-Radiator-Fan-Install-with-DC-ControllerGranted it does not have to be that complicated but I like what I like. Hope that helped. Darren Quote Selected
Cheap Mark 8 Fan Controller Reply #13 – October 28, 2011, 02:19:32 PM Tom...can you be a little more specific on the fan supplier? Quote Selected
Cheap Mark 8 Fan Controller Reply #14 – October 28, 2011, 02:58:31 PM Quote from: TOM Renzo;371336Thanks Darren that is an interesting GIZMO. I like the fact that it eases on the fans so the current is controlled. Interesting GADGET. Who makes it. I am interested in it as a product to install and make some extra cash. You know the American mind set in me. Thanks http://www.dccontrol.com/From what I gather, these are fantstic, but the owner of the company is a pain to deal with. Tons of stories of people paying and taking months to receive product. If you wanted to rep them, Id keep a decent quantity on hand. Quote Selected
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