Contour Fan Wiring...

When in doubt, see what size wiring and circuit protection was used from the factory on the donor car.

The size of the relay does matter. Too small of a rating is bad. Too large is generally ok.

If you don't have a high current alternator, you can forget about using an electric fan in the car. The stock 65 amp alternator isn't big enough to run the fan and the rest of the car.[/b]

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

Fuse links come with a current rating just like fuses. A clue as to what current they are designed for is to look at the size wire they protect.

Choose the fuse according to the wire size.

Wire size current table:
18 gauge wire = 5-8 amps
16 gauge wire = 10-12 amps
14 gauge wire = 15-17 amps
12 gauge wire = 20-25 amps
10 gauge wire = 30-40 amps
8 gauge wire = 50-60 amps.

Keep in mind that the wire size in the chart is for the circuit itself, not the size of the fuse link. The packages of fuse link repair material you can get at the auto parts stores also will have a current rating on them.

See Ford Fuel Injection How To Solder Like a Pro for some excellent tips of soldering wires for best electrical performance.

Aircraft type circuit breakers are designed for low voltage DC applicaions and would be an excellent choice to replace fuse links. They come as a push/pull to reset button, and range from 1.5 amps to 60 amps and higher.

See Pilot Supplies, Avionics, and Homebuilt Aircraft Parts from Aircraft Spruce and Specialty Co. or http://www.wicksaircraft.com/catalogDetails.php or Home for circuit breakers and other items.


Fan controller options:
Switching a fan on and off manually is a bad idea. Too many guys have been distracted (hot girl kissing on their neck, too much to drink, dog tired and not thinking clearly) and cooked things because they forgot to flip the switch. An equal number have forgotten to turn the switch off for the same reasons and run down their battery.

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 FAN-PWM. 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.

Do not use a simple on/off switch without using a relay. The current load can burn up the typical cheap automotive switch very quickly. The fan draws 30+amps and you need to use #10 wire on the fan power and ground wiring.

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.

The steady state current is about 30-32 anps. The startup spike is what causes problems. It can run 2-3 times the steady state running current. The spike lasts for less than 3 seconds, but it plays havoc with the available current and voltage for those 3 seconds.

Use 10 gauge wire for wire runs of 10 ft or less and a 30 amp slow blow fuse.

Wire size chart follows...

1991vert said:

thanks a lot. i just don't want my car catching on fire


edit: do i need to run a diode?

Click to expand...

The diode is recommended to prevent the electrical surges from damaging the computer, radio and any of the other expensive electronics you may have in the car. At less than $2 its a no brainer. Put it in and save yourself some aggravation.

This is not the best way to wire up the circuit. The EEC isnt reliable for energizing a relay coil, and you'd want terminal 30 going to a fused battery source. A switched source is not necessary because you use the EEC to trigger your relay, so it can't trigger if the ignition is off.

1991vert said:

well it looks like this has an initial start up spike of 100amps...with this in mind, is it okay to run it like this?

75 amp relay, no idea with the fuse.

p.s. i'm not an electrician

Click to expand...

HISSIN50 said:

This is not the best way to wire up the circuit. The EEC isnt reliable for energizing a relay coil, and you'd want terminal 30 going to a fused battery source. A switched source is not necessary because you use the EEC to trigger your relay, so it can't trigger if the ignition is off.

Click to expand...

That circuit will work on a 94-95 5.0 Mustang, but not on an 86-93.

The computer does not have the control circuit built in to control the relay. I tried using a similar one that I downloaded from http://fordfuelinjection.com/files/A9L_E-Fan_How-to.pdf .
I found that the pin 41 they recommended to use did not change states with changes of engine temperature. I was very careful to follow the test instructions to make sure that I didn't miss anything.

If you have a different pin configuration or reference tech note, we all would like to see it.

jrichker said:

That circuit will work on a 94-95 5.0 Mustang, but not on an 86-93.

The computer does not have the control circuit built in to control the relay. I tried using a similar one that I downloaded from http://fordfuelinjection.com/files/A9L_E-Fan_How-to.pdf .
I found that the pin 41 they recommended to use did not change states with changes of engine temperature. I was very careful to follow the test instructions to make sure that I didn't miss anything.

If you have a different pin configuration or reference tech note, we all would like to see it.

Click to expand...

The 94-95 EEC has output circuits to energize relay coils (they are not even the same polarity, and the default is to have low speed on. The EEC shuts it off when it should not be on) but if you were to not use those, you still cannot use the ECT circuit [AFAIK] to trigger a relay coil. The latter was how I interpreted his diagram.

Just the variance in relay coil resistances would make using a thermistor signal a difficult proposition IMHO.

1991vert said:

i do not run a stock computer. i run an aftermarket Big Stuff 3

Click to expand...

I missed this. In that case, I dont have a clue how your EEC works or what provision it has for fan control. All I saw before was a '91 vert, and my previous reply was based upon that.

1991vert said:

haha ya i dont think i mentioned it and i had to read your reply a few times, then it clicked

how do i go about wiring this diode in? should i use a terminal block and wrap the diode around the screw?

Click to expand...

Jrichker's the diode expert and one who mentioned it earlier. The diode is used to quell inductive loads, so it's reverse biased across the motor leads. If you hook it up forward-biased, it will fry when the fan powers up.

I like to install them in the wiring connectors (with the load-wiring) right at the fan motor. I dont know how Jrichker does his, but if his method differs, go with his.
As his diagram shows, the anode goes on the negative side and the cathode goes on the positive side.