Electric fan install questions...

no you need to use at least 40 amp relay or a 30 amp, yes you need to put an inline fuse b/t the power and the relay.

you can get the 12V from alot of places but the easiest is at the radio

The Mark fans spike up to 90amps on startup...they need a much bigger fuse than the Taurus fans. I'm currently running a 125amp car stereo fuse setup with mine PLUS the plug/fuse setup that i got off of another Taurus fan (turned out the plugs were exactly the same, so the extra fuse is just good measure).

As for that write up...the whole test fitting stuff is overkill. Just trim 3/8 off the shroud. NO MORE, NO LESS. Measure twice, cut once and don't mess it up. If in doubt, cut 1/4 inch and see if that works for you and if not then cut another 1/8 extra. I trimmed 3/8 off mine and i have plenty of space between the water pump pulley and the fan.

90 amp spike need a big relay

Yeah that's just on start up...i'm not sure what it pulls while it's just running...startup is really crazy though. We found this out after blowing a few 60amp fuses.


I can't stress enough how important it is that you don't trim too much off the shroud. If you cut off too much the blades will contact your radiator and you'll have ruined the fan.

does anyone wire in a Capacitor with there fan to take the brunt of that start up load?

I've thought about it...but more to take the load off the alt than take the load from start up. I'm just too lazy to try it and i haven't noticed any drawbacks to not doing it.

you would probably just need .5 Farrad or so

The battery has plenty of reserve for the start-up draw. It's just a burden on the wiring and makes fusing cumbersome. I like to use links instead of fuses.

links?? please explain or provide pictures

S&B said:

links?? please explain or provide pictures

Click to expand...

Fusible links.

Make sure you use the right gauge wire. If you're gonna run it constant, it's gonna get HOT and could easily melt the wires.

Though they draw little power, I would be sure the LED is not powered while the car is off.

Using two relays in parallel isnt the most robust idea. You don't want fan issues while driving in traffic. For dinky SPST/SPDT relays, use a flyback diode in your fan installation.

Why dont you wire the LED when the fan is ON?

This is how I wired my Taurus fan, I would've used the Mark VIII fan, but it didnt fit. If I can ever get the Mark VIII fan to fit then all I have to do is change harnesses, and maybe step up the fuse to a 50 amp Maxi. I've been DD with this set up since July 08, Ive been through town, highways, and city traffic and the fan has been the least of my worries.

This is the diagram I found, I modified it a little to suit me. I'm using the 75 amp Bosh relay for the fan load, the a/c relay is a dinky 30/40 amp; and I'm using a GM fan switch that I bought from a Corvette site.






Oh and here's another write up if you havent seen it. http://www.geocities.com/smithmonte/Auto/MarkVIII_Fan.htm?20074




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If you don't have a high current alternator, you can forget about using an electric fan. The stock 65 amp alternator
on 86-93 Model Mustangs isn't big enough to run the fan and the rest of the car.

3G 130 amp alternator installation instructions: Stangnet 3G install sticky 3G Alternator Install: A How To - Mustang Forums at StangNet

The best fan controller available today is a DC Control unit. Now serving. Cost is about $110. Be prepared to wait 4 weeks or more to receive your controller once you have sent in your payment. The controllers are custom made in small lots and lead times can stretch out.

Next best is a SPAL controller - $70-$90 See http://www.spalusa.com/fans/automated/accessories/fanpwm.html. Ebay will have the controllers for the $70: do a google search and see what you find.

At the bottom are the Hayden or Imperial controllers available through Advance Discount Auto Parts and AutoZone. The non adjustable one is about $30 ( Hayden 226206) and the adjustable one is about $60 (Hayden 226204). I recommend you do a Google search on Hayden and the part number for more info.


If you are good with electrical stuff (90% of the people here aren't), build your own controller. The numbers on the diagram (#86, #87, etc) refer to the numbers on the bottom of a typical automotive relay.



Note that the thermostat switch in the diagram isn’t really suited for the job. You’ll have to do a Google search and find your own.

This version of the fan controller will continue to run the fan after the ignition switch is turned off, just like most new cars.

To allow the ignition switch to control the fan so that it does not run when the ignition is off, connect the relay contact #86 to the red/green wire on the ignition coil or to the red/yellow wire on the coolant level sensor.



If you are an experienced electronics tech or electrical engineer, email me and I will send you the prototype drawings of a fan controller that is probably as good as the DC Control unit. It is a build it, troubleshoot it yourself item. I will not build or troubleshoot units, so it is not suitable for anyone who isn't really good with electronics.

Alternate placement for a temp gauge sender or temp switch/temp sensor for an electric fan. Use the heater feed that comes off the intake manifold. Cut the rubber hose that connects the manifold water feed to the heater and splice in a tee adapter for the temp gauge sender. Be sure to use the same water feed line as the ECT sensor. That way you will get the most accurate temp readings.

Tee adapter info:
Make a pilgrimage to your local hardware or home supply center and get some copper pipe and a tee that fits the temp gauge sender. Solder two pieces of copper pipe onto a copper pipe tee with threads in the tee part. Find the correct brass fitting to match the temp sender threads to the tee fitting.