General Index
[1 - Overview] [2 - My wreck!] [7 - Crazy Robin!] [9 - Candy's Ranger] [10 - Keypad entry system]

Meets and Outings
[11 - Centralia adventure Part I] [21 - Centralia adventure Part II]

How-To Articles
[3 - Overhead Console Install] [4 - Overhead Console Wiring] [5 - MAF mod] [6 - LED switch mod] [8 - Homebrew Remote Bass Control] [12 - Headlight/4x4 Switch LED Mod] [13 - General LED tutorial] [14 - EATC install how-to (pages 14-19)] [20 - IAT Resistor Mod (older engines only)] [22 - Automatic Power Windows] [23 - Cruise Control Pod LED's]

The Ford Explorer Electronic Automatic Temperature Control (EATC) Mod

The next about 5 or 6 or whatever pages (as I write this it's not complete) will describe in detail the retrofit of an Explorer EATC to a late model Ford Ranger. Any Ranger from 1995 on should be able to be wired, though the how-to is focused on 1998 and later. I've decided to be rather verbose about this to make sure it's well understood what we're up to. I really don't mean to scare anyone with the number of pages -- I just want to get as much information in your hands as I can reasonably (or have the patience) to do.

General Information and History

First, let me say that this may be one of the more pain-in-the-neck (literally for me as I have spinal arthritis, lol) mods you may ever do electrically. It involves some rewiring, refitting, and minor cutting, drilling and sanding. I know my keypad mod requires you to cut a hole in the door; but this mod requires much more WORK. Still, I'd say it's well worth it for the look, but especially for how comfortable it is. It can end fights with your significant other over the heater (though maybe not entirely). It maintains a constant temperature very nicely, blowing only as much air as needed to maintain it which keeps the sound level under control also. That's my unit to the right.

The units below are pictures of two others I put in. The one on the right IS a Ranger, but it has a custom center bezel.

The EATC first appeared in the Explorer in 1995. The original unit received input from 3 sensors: outside air (ambient) temperature, cabin (interior) temperature, and "sun load". The sun load sensor tells the EATC how bright the sun is shining in on the dashboard so it can anticipate heat load in the front of the cabin. It also had auxilliary control modules to control fan speed over an "infinite" range of speeds, and to control the blend door (which controls the discharge temperature of the air blown into the cabin). It can also control where the air is sent -- defroster vent, panel vents, floor vents, etc. in any combination.

In order to ensure that the cabin temperature is accurately sampled, a vent was placed above and to the left of the glove compartment, high on the face of the dashboard. Placement is only part of the issue -- you have to ensure that the sensor sees that actual air temperature of the cabin. Ford made an "aspirator" that draws air through the sensor assembly using suction from the intake side of the blower motor. This creates a continual "draw" of air past the sensor that comes through the vent from the cabin, helping the EATC to better know the "real" temperature of the cabin.

Using the temperatures and sun load information, the EATC anticipates required heating and cooling requirements, and continually adjusts fan speed, discharge temperature, and where the air is sent. It makes very good decisions about how to keep the occupant comfortable, but the driver can override it and manually direct the air and fan speed.

In 1996 the ODB-II vehicle emissions standard specified an in-vehicle network for data communication between control modules. Ford added an OBD-II network connection to the EATC in 1996 to take advantage of this. The ODB-II connection allows the EATC to query the PCM for engine coolant temperature and vehicle speed. Using this information, the EATC can provide extra comfort features like not blowing air in the winter until the heater can produce heat, and anticipating drafts and extra cooling that may occur when the vehicle is in motion.

In 1998 Ford changed the design slightly and used that design all the way to 2001. It changed the pinout of the connectors somewhat, but not what the unit does. What this means is that 1995-1997 units and 1998-2001 units are NOT plug compatible, even though the plugs fit -- rewiring is required.

2002 units have a completely new design for the head unit and there is NO COMPATIBILITY AT ALL with the earlier units.

In addition, in 1998 the blend door actuator changes and uses a slightly different connector which once again FITS but is WRONG between the two year ranges. Also, Ford changed the connector on the fan speed controller to reduce corrosion in 1998 or so. When you pull pieces from the junkyard, MAKE SURE YOU GET THE PART AND THE HARNESSES WHICH GO WITH IT.

The 1995, 1996, and 1997 units all have blue displays and lighting. They also share a common connector pinout that is different than later units, as I've already noted. The 1998 and up units have green displays ang lighting. I'll provide a page describing the differences between the two year ranges in another page.

One final note: the units used in Taurus, Sable, Crown Vic, Marquis, and Lincolns are different and I'm not going to describe them. They are not as desirable for our purposes. In addition, Lincoln Navigators have the same system as the Lincoln automobile which uses PWM fan control which is not compatible with the analog control units -- except that the analog ones can be modified if you are willing to do surgery on the EATC "head unit". I may make a page on how to do this. I like the Lincoln fan controller much better -- it doesn't get hot, doesn't mount in the ductwork, and may last forever.

That summarizes the basics on the EATC unit. Go to the next page for information about what you need to do this mod.

Some additional references

Page describing swapping EATC into a CrownVic -- good for information on the general system and peripherals but not all the details of a Ranger install. Still, these pages were INVALUABLE for helping me understand what was involved and I'm indebted to the author. I've emailed him thanking him but never received a response -- I bet he gets a lot of emails, lol!

Ryan Hooks' site with information on EATC -- Ryan is a fellow experimenter and contributed to this how-to.