- Joined
- June 3, 2003
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- 3,293
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- City, State
- Austin, TX
- Year, Model & Trim Level
- OBD-1 Kenobi
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!
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!