Head Unit Details

(To the right is my unit at night, a blue lighted 1997.) As I've mentioned already, the control heads come in several "flavors" and the only one we're concerned with here is the Explorer/Mountaineer version. Navigators and automobile head units are different and though they can be adapted, it's too much to describe in a simple how-to. If you're the experimental type like myself and they offer you an advantage, then give them a try -- particularly if you have prints on the wiring to verify that the color codes match the truck units. The connector pinouts are DEFINITELY different.

The first thing you can do to get the proper head unit is to take it from the proper donor vehicle! But sometimes deals come along and we aren't the one who pulled the unit. To help you identify which kind you're dealing with, here's some information:

1. Explorer style units have a button on the upper left of the console that says "REAR FAN OFF". On automobile units it says "OUTSIDE TEMP".

2. 1995 to 1997 units have blue displays (because of a blue display filter window). You can shine a flashlight into the display window to see what color it is. 1998 through 2001 units have a green display filter.

3. 1995 units lack two wires towards the end of the black harness connector. They are TN/OR (tan/orange stripe) and PK/LB (pink/light blue stripe). These are the ODB-II network wires which were not present in 1995.

4. Pin 23 is unused on controllers intended for analog fan control units and there is no wire there. On units intended for digital PWM fan controllers, pin 23 has a TN/OR wire on it. (See connector views below). For this mod you do NOT want a PWM fan control model.

5. 1998 and later head units have a yellow wire completely lacking in earlier years. This wire is for the steering wheel controls for the radio and heater found on later Explorers. To use it would require changing both your steering wheel and "clockspring" mechanism (which feeds signals to/from the wheel so it can turn) to those of an Explorer. If you want to try this part of the mod, you definitely need a 1998 to 2001 unit.

6. 1998 and later units have a YE/BK wire to control power to the blower by switching the fan relay on or off. Previous years simply jumped "hot in run" 12 volts to the fan relay, turning it on whenever the key was on. However, if the fan controller were to fail to "full on" (likely possible failure mode), then your fan would run full blast whenever you started the vehicle. With the relay control line, the head unit can turn off the fan when you hit the "OFF" button.

In the connector diagrams below, what is called the "white" connector is usually more of a gray color.

Here's the pinouts of the connectors. Note that the connectors for 1995 do NOT have the DLC/SCP data bus (ODB II communication wires). These wires are easily distinguishable because they are twisted together to make a "twisted pair".

1995 through 1997

1998 through 2001

IMPORTANT NOTE: The pinout shown above for the 1998-2001 BLACK connector has an error. Pin 6 shows a LG/B wire and it is in fact LG/OR. The schematic, and actual observation of units confirms that it should be LG/OR. Thank you, Bob, for pointing out that Ford's diagram was in error!

What to get with the controller

You MUST get the harness connectors and at least 6" or so of wire if you possibly can. If you don't, then you must try to get the harness off a similar year vehicle because of the wiring differences. Besides that you REALLY MUST get the vacuum harness. Explorers and Rangers use the same basic heater ducting and control setup. The "doors" to direct the air are all vacuum controlled. The EATC controller has vacuum valves built into it to electronically control the routing of air inside the ducts.

The vacuum harness is screwed to the back of the controller and does NOT need to be removed from it. You can see it with all it's multi-colored tubes in the center of the back of the controller in this picture.

It should be unplugged from the ductwork where it connects behind and to the left of the glove compartment. 2 white tabs hold the blue rubber end connector of the vacuum harness in place. You don't need the white piece. You can see where it plugs in at the lower left of this picture. DO NOT REMOVE THE INDIVIDUAL TUBES. The tube harness is clipped to the dash frame in a couple of places so pull those nylon retainer pegs loose and when it's free you can pull it out with the controller when you remove it from the donor vehicle.

DON'T BUY A UNIT WITHOUT WIRING AND VACUUM HARNESS UNLESS YOU ARE DESPERATE!

Organizing the "Rat's Nest"

For me, especially when colors are duplicated in a harness, I like to group wires by function. It helps me to organize the terminations and make fewer mistakes by terminating one sub-system at a time. You may find this helpful as well and so I'll share what I did. As you can see from the photo to the right, there are a lot of wires -- but they become more manageable when you break them down into groups. I just use masking tape and mark something on each "flag" to identify what bundle is what.

So here's how I usually group them:

Power and ground:
BK - ground
RD - English/Metric (+12 volts = English, ground = Metric)
BK/LG - "hot in run" (switched +12 volts)
WH/PU - "hot in run" (1995-1997 only)
LG/YE - "always hot" (constant +12 volts)

Blend door actuator/servo motor
OR - Blend door drive 1 (CCW)
DB/LG - blend door drive 2 (CW)
BR/WH - blend door position feedback
OR/BK - blend door ground
LG/OR - blend door +5 volts

Fan relay and speed control
WH/PK - "High speed" bypass signal to speed control
BR/OR - blower speed controller input signal
TN/OR - blower speed feedback (do not confuse with other TN/OR)
YE/BK - blower motor relay control (1998 up only)

Sensors
PK/BK - ground (common) for all sensors
RD/OR - ambient (outside) temperature sensor
BR - sunload sensor input
WH/OR - in car (cabin) temperature sensor

Miscellaneous
YE - steering wheel controls (1998 up only)
LB/RD - dimmer input
RD/BK - dimmer input
RD/OR - rear fan relay (we'll use to disable A/C compressor)
PU - A/C compressor demand signal
TN/OR and PK/LB - twisted pair for network tie in (1996 up only)

Please note: There are two RD/OR wires, and two TN/OR wires. You MUST ensure you put them all in the correct groups. Use the connector pinout diagrams for your year console to sort out which one is which.