How To: Install Electric Fan WITHOUT going aftermarket (Let the PCM do the cooling!)

Hello again fellow forum members. Following on the heels of a Message Center install and a 5R55E swap, I was trying to decide on yet another blasphomous electrical frankenstein-esque project to start working on. So while out at the salvage yeard yesterday, I ran across a 96 MK VIII that had some tan switches I wanted. Then while I was there, I started looking at the cooling fan and decided 'huh, might as well get one' since I have been wanting to do an electric fan conversion on Blue for some time now. So I pulled it out, took it home, and started doing research.

It seems that everyone that has done this install (even non-explorer guys, just EVERYONE in general) uses some sort of aftermarket controller to run the fans. While I am sure that these are good quality devices, some of the installs just look...well, not stock (and I am big on things trying to look stock).

So I got to thinking that there must be some way to use a factory ford fan controller out of SOMETHING to make these fans work using stock PCM outputs. I know what some of yall are thinking...'The explorer PCM doesnt have any programming to output lo/high speed fan commands' and you all are right in every way...except one

May I introduce to everyone something called the Variable Load Control Module:


This little guy is found on 94-96 Lincoln MK VIII's (the same one you pull the fans from!) and it controls the cooling fans..as wll as A/C clutch and fuel pumps. But for our purposes, we will just concentrate on the cooling fan operation.

I know what you are thinking next: "Well sure Russ, several ford vehicles have some sort of module controlling the fans, but you still need PCM outputs to tell it what to do!!" Again, you all are absolutly correct! Except that all those other modules recieve input from the PCM via dedicated circuits for lo/high speed fan control (Typically on OBD-I, pins 13 and 31, and OBD-II, pins 45,46). This is where the VLCM differs...

Here is the wiring diagram for said VLCM...Just study it for a moment...



Get a good look? One thing you might notice is that the PCM has no dedicated circuits for the cooling fans! So how does the PCM tell the VLCM to turn on the cooling fans? The SCP network

You see, all first gens (and OBD-I for that matter) have something call the SCP Network (Standard Corporate Protocol, a ford specific variation of the SAE J1850 communications link type), with allows data to be transferred over a twisted pair of wires. It is this network that let's code readers "read" fast codes, and really high end scanners (Ford NGS) read PID data. And it is this network that allows the VLCM to "read" the PID data (Just like a scanner) being sent out by the PCM, thus the VLCM commands the cooling fans on and off based off the PID data. For instance:

I can hook up my NGS scanner to Kris Guilbeax's 1991 Eddie Bauer Two Door and start running the engine. I then start monitoring the PID values that are available (Barometric pressure, ECT in degrees, IAC in degrees, RPM, ect ect). With a VLCM installed, it too will see the same data that NGS is displaying. When, say, the ECT PID (engine temp) reaches 200 degrees, the VLCM 'sees' this, and turns on the cooling fans. And since all OBD-I vehicles use the same SCP network protocols, this information is being broadcast all the time, ergo.... wait for it...

A first gen Explorer PCM can run a MK VIII Fan controller, thus running electric fans without use of going with aftermarket controllers..

So where does this leave us? Well, right now this is all in the experimental/theory/discussion stage. I still need to get a VLCM and hook it up and look to see if this all actually works. If it does, wonderful. If not, eh, I'm not out much.

So Discuss!

Subscribing. Work your magic!

Ditto..

What bothers me about using all these aftermarket controllers out there now is that they don't handle the a/c well. They all seem to just want to run the fan if the A/C is on which is worthless if your doing 60mph down the freeway.

I really want it to know that your doing 60 mph down the freeway with the a/c on and the coolant is getting enough air flow so don't turn on the fan while at the same time it can figure out that we are doing 25 mph in town with the a/c on so turn on the fan to keep the a/c cool.

~Mark

Maniak said:

Ditto..

What bothers me about using all these aftermarket controllers out there now is that they don't handle the a/c well. They all seem to just want to run the fan if the A/C is on which is worthless if your doing 60mph down the freeway.

I really want it to know that your doing 60 mph down the freeway with the a/c on and the coolant is getting enough air flow so don't turn on the fan while at the same time it can figure out that we are doing 25 mph in town with the a/c on so turn on the fan to keep the a/c cool.

~Mark

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And that's where the 'Variable' in Variable Load Control Module comes from. See, the output voltage to the fans is VARIED, meaning its not always full on when it doesnt need to be. The VLCM monitors the AC request PID as well as the VSS signal that is on the SCP network, and determines fan control based off the programming that it has. So in that instance above, if the engine is staying at an OK temp with the a/c on and going over 45 MPH, then as long as the temp stays below 195 degrees, it wont kick the fan on.

you guys are seriously overthinking this.

and the AC request doesnt actually need anything special at all.

the last thing youd want is your ECM controlling your E-fan.

Thuggsy said:

you guys are seriously overthinking this.

and the AC request doesnt actually need anything special at all.

the last thing youd want is your ECM controlling your E-fan.

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Would you mind elaborating? I'm want to hear pros and cons of course, that's why i listed this as a discussion phase right now. Thanks!

Thuggsy said:

you guys are seriously overthinking this.

and the AC request doesnt actually need anything special at all.

the last thing youd want is your ECM controlling your E-fan.

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How would you use an off the shelf, after market fan controller to run the e-fan and not do it inefficiently?

Every fan controller I've seen uses a single a/c signal wire and if it is told the a/c is on it runs the fan. That means the fan can be running when you don't want it running. An example is when you don't want it is when your heading down the freeway at 65mph with the a/c on and the coolant temp is staying at 160F (radiator output temp) just from the air movement.

I've looked into trying to mix together a speed controller to the mix so the fan would not turn on just because the a/c is on while the speed is over 45 mph.

The few ways I was leaning towards would have been expensive so I just went with a manual switch to turn off the fan control from the a/c. The worst that will happen if I forget to flip the switch is the a/c gets warm when I stop or go slow. The fan will turn on based on coolant temp so I don't have to worry about over heating it when I forget to flip the switch back.

As I see it, using the PCM with other OEM parts is the "correct" way to do it. Of course, for most people, understanding how the parts really work and to make them work on a different vehicle is a daunting task (even for me). I'll let NICE59FORDF100, who understand Ford electrical, figure out what goes where and to test it out.

~Mark

Maniak said:

As I see it, using the PCM with other OEM parts is the "correct" way to do it. Of course, for most people, understanding how the parts really work and to make them work on a different vehicle is a daunting task (even for me). I'll let NICE59FORDF100, who understand Ford electrical, figure out what goes where and to test it out.

~Mark

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Thanks for the vote of confidence! I will do my best

you should use a (Hayden) fan relay and a "temp sensor switch" in your coolant system (heads or intake) to activate (ground) the relay.

the temp sensor switch should be rated the same or a little higher then your thermostats opening start point. (185* thermostat = 185* switch etc)

optionally you could install a manual over-ride switch too.

the AC needs nothing.
the added load of AC will keep your coolant @ thermostat temp, fan will come on if its needed.

cars can run w/o fans above 30MPH, no need for fan(s) to be on while moving.

using the ECM for this is a BAD idea, very bad.

Thuggsy said:

the last thing youd want is your ECM controlling your E-fan.

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You do realize that pretty much every car with an OE electric fan is controlled by the ECM right?

You are correct, that is how you wire in an aftermarket fan controller, and in fact, that has been the way it has been done for these situations. But in my original post, i mentioned I am trying to find a way to make this more stock without having to add override switches, ect to the interior that would not look stock. And the good thing about using a VLCM is all the built in relays and solid state controls were specifically designed for the MK VIII fan, and thus, are rated accordingly.

Thuggsy said:

using the ECM for this is a BAD idea, very bad.

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And why is this if I may ask?

NICE59FORDF100 said:

You are correct, that is how you wire in an aftermarket fan controller, and in fact, that has been the way it has been done for these situations. But in my original post, i mentioned I am trying to find a way to make this more stock without having to add override switches, ect to the interior that would not look stock. And the good thing about using a VLCM is all the built in relays and solid state controls were specifically designed for the MK VIII fan, and thus, are rated accordingly.



And why is this if I may ask?

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you actually trust this computer controlled garbage?

what i posted is how i used an electric fan in a non-computer car. (1985 Corvette)

Thuggsy said:

you actually trust this computer controlled garbage?

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Well, yes, yes I do. Considering it hasnt given me any problems in the 20+ years my truck has been on the road, I'm fairly certain it will handle fan control just fine Besides, my 92 is actually running 2 PCM's and even that is working pretty darn good lol

Thuggsy said:

the AC needs nothing.
the added load of AC will keep your coolant @ thermostat temp, fan will come on if its needed.

Click to expand...

The above is the part I don't understand.

The A/C will get warm way before the coolant temp comes up enough to turn on the fan if you don't hook the a/c wire on the Hayden controller.

The part I see missing with the hayden controller (or any others I've used/looked into) is that they don't have a way to make the fan not run when the a/c is on AND your coolant is is cool enough (e.g. your at 45 mph or higher). With the a/c wire hooked up on the controllers the fan is "on" no matter what the coolant temp or speed.

~Mark

Maniak said:

The above is the part I don't understand.

The A/C will get warm way before the coolant temp comes up enough to turn on the fan if you don't hook the a/c wire on the Hayden controller.

The part I see missing with the hayden controller (or any others I've used/looked into) is that they don't have a way to make the fan not run when the a/c is on AND your coolant is is cool enough (e.g. your at 45 mph or higher). With the a/c wire hooked up on the controllers the fan is "on" no matter what the coolant temp or speed.

~Mark

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And Mark, I do believe that the VLCM method would actually achieve that for you, but further testing is needed of course

I've been waiting to see you do and electric fan install on a 1st gen. You have a far great understanding of electronics than most on here so I'll be following along and probably use some of your info on my own fan install one day.

willindsay said:

I've been waiting to see you do and electric fan install on a 1st gen. You have a far great understanding of electronics than most on here so I'll be following along and probably use some of your info on my own fan install one day.

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Thanks! Hopefully Ill have something to test in the next couple weeks. I recently aquired a 60-pin breakout box so that will make things go a little quicker. As soon as I get my hands on a VLCM, I'll be able to tell for sure.

Nice59, as always, you are a genius. I'll be watching fervently in case I ever get smart enough to go back to a first gen again. For now, I was just going to use an Arduino for a fan controller, but this looks like the easier way to go.

Thuggsy said:

you actually trust this computer controlled garbage?

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Drives a '97 EX-XLT 4.0 OHV

...

You know, computers are and have been controlling far more failure prone and important components in cars since the late 70s and early 80s... Guess what tells your fuel when to be pumped, and when to go into your engine?

If you have ever tuned cars run entirely mechanically and by vacuum, you would realize that these computers do a lot better job of it than the old stuff.

FIND said:

If you have ever tuned cars run entirely mechanically and by vacuum, you would realize that these computers do a lot better job of it than the old stuff.

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A/C cooling adequate

At slow vehicle speeds the fan is important for cooling the engine coolant via airflow thru the radiator and making the A/C cooling adequate via airflow thru the condenser. I wonder if the VLCM monitors the IAT and compares that with the desired cabin temperature versus the actual cabin temperature and adjusts the fan speed accordingly. Or it may just assume that if the vehicle speed exceeds a certain value the airflow thru the condenser is adequate and there is no need to run the fan. I agree with Maniak that most of the fan control problems are integrating the A/C cooling, engine cooling, and fuel economy. I think the electric fan on my 1996 Volvo 850 Turbo Wagon is a two speed (off, low, high) with a fairly dumb controller but seems to work fairly well. I know that it responds to engine coolant temperature. I don't know if it is vehicle speed dependent.