Have any Ford service manuals? Electric Fan Questions.

[HarryH3]

So I was poking around under the hood of a 3.8 liter Taurus at the junkyard last week. You know, the one that has the 2-speed fan that seems to burn up normal relays with its massive current draw. I unwrapped part of the wiring harness to find out where the power feed for the fan comes from. The ground wire from the fan is a heavy one, that connects directly to the negative battery cable. /forums/images/graemlins/eek.gif However, each of the power wires split off into two wires just before the control module that is mounted just above the fan. So I have a few questions...

Does the factory service manual show what is inside that control module? I'm wondering if they have two relays inside for each circuit of the fan, or do they use electronic switching?

Does the low speed power stay on when the fan switches to high speed mode, or does the low speed circuit switch off?

What else does this module do? It has far more wires connected to it than are needed just for fan control.

Does anyone have some drawings that they could scan in?

 

[POWERMAD]

My scanner don't work but I have a wiring schemetic for it. A resistor is used to control fan speeds.
Sorta like the heater fan. It's called a fan dropping resistor.
Low speed is engine cooling and when the high side a/c switch gets to it's set point it sends a signal to the module that kicks the fan on high..
Typical Ford stuff. My Mustang has a module to conroll the fan, I wired in a relay and manual switch to conrol the fan. I had to use a 40 amp relay and 10ga wire after burning up a smaller relay and wire. They pull alot of amps.

 

[dyeager535]

Since it's the same fan (unlike a dual setup) if noise isn't an issue for you, I'd probably seriously consider running it at "full speed" without wasting time on the resistor circuitry.

A slower fan speed will do nothing but increase the amount of time it takes to cool the fluid in the radiator, so unless noise is an issue (less fan noise, plus less cycling on and off since the cooling isn't happening as fast) I don't see a single reason to run a two speed fan.

I've got dual fans, so I was *contemplating* running both at the same time to reduce the wiring complexity, but I knew how cool my engine ran before, and I figured I would wire up the second fan as factory had intended, (excluding the AC part of the wiring circuit) as a backup in case the primary fan just couldn't cope.

Then again, I guess if your current setup runs cool and you suspect even on the low setting cooling will never be an issue, you could run the dual speed fan the same way, reserving high for "emergency"/abnormal situations. Quite a few applications use many different one wire temp switches for fans, you could use a low temp one for the low speed fan, and one only 10* or so above that for the secondary fan. Obviously that setup would only be worthwhile if your coolant temps are easily managed.

If you can't tell, I spent a bunch of time contemplating how best to run the fan setup, at least in my eyes. /forums/images/graemlins/smile.gif

If you were just asking because you are curious for what all the wires were... Not sure how the Fords were run, but the GM setup I have uses around 9 wires total in the dual fan setup...2 direct battery feeds to the switched sides of both relays, 2 12V to the fan motors for the switched side of the relays, 2 grounds for the motors, 2 ignition 12V for the relays "switch sides", 1 wire for the ECM controlled primary fan, and 1 wire to the secondary fan switch in the head. (both the ECM and temp switch just ground the circuit) The AC pressure wire is inline of one of the above wires, so it isn't "noticeable" where both relays are.

 

[HarryH3]

What year is your Mustang? Does it have 2 wires going to the fan motor, or 3?

This fan has 3 wires and runs slow when 12 volts is applied to the low speed wire and runs fast when 12 volts is applied to the high speed wire. If it was using a dropping resistor, there would be no need to run 3 wires to the motor (Ground, low speed, and high speed). The resistor would just be inserted into the power wire for low speed. Hmm, did Ford use different approaches in different years?

 

[HarryH3]

Dorian, my plan is to let the fan run on slow speed most of the time, controlled by the ECM. During the winter especially, it won't need to run on high speed often. While driving in winter it would probably never come on at all. But sitting traffic, or waiting somewhere with the heat running may require it to kick on from time to time. And yes, running it on low will keep the noise to a minimum. /forums/images/graemlins/cool.gif

I'd wire the high speed circuit to kick on when the GM aux. cooling fan switch kicks on.

 

[POWERMAD]

Harry
The stang is a 92. At the plug there is just 2 wires.
I tapped into the fan side of the plug.
The fan has never worked and after locating the fan modual and finding out that it is a dealer only item I just brought home some stuff from work to kick on the fan when needed.
For the Tuarus integrated control modual circuit it has connected to it...
Automatic temp control.
2 A/C inputs.
ground.
2 inputs for the cooling motor.
2 inputs for the dropping resistor, which has it's own 14ga fuse link hot at all times.
input for the inertia switch.
Hot in run
then a few from the ECA and self test output connector.
86-95 Taurus schematic BTW.
Of course the schematic is labled typical integrated control modual circuit.
As far as changing who knows what over the years it's entirely possible.
When the version 2 Volvos hit the market we got all the latest and greatest manuals.
To bad they changed a bunch of stuff we didn't know about.
I had one that came in because the fan would not come on with the A/C on.
First one I had to deal with, they now have 3 ECU's to control the climate control.
The values in the manual for the switches was not the same as in the rig.
So after spending 6 hrs checking and replacing good switchs and just scratchin my azz I hooked up the laptop and found that the fan had not been enabled for A/C operation. DOH /forums/images/graemlins/blush.gif
A few weeks later we got the revised bullitin. /forums/images/graemlins/tongue.gif
Gotta love progress.