Initial wiring and testing

You may be saying, "John, what do you mean initial wiring?" Well, the idea is to get a 12 volt power supply that can do 4 amps at or more, wire this thing up on a workbench or table INDOORS, and test all your JY finds. It's really a good idea to make sure everything works BEFORE you whack off cable connectors in your truck (which you will be doing). When you install this thing -- it's not so easy to go back again.

Mainly what we will do is break down the harness into wiring "groups" (see previous page) and then terminate those groups.

The one thing we can terminate in a finished form is the blend door servo. You just need about 18" to 24" of wire from the head unit to easily reach the servo location when installed.

Servo harness construction

You have several options for making this harness. You can go all out and make it by soldering it and putting heat shrink on the splices, or you can just use small crimp on "butt splices" or just about any method to make this small section of harness. I DO NOT recommend the "twist and tape" method. That's going to be a dead end -- don't do it. We will do that for out temporary hookups; but for this particular bit, lets do it right.

However you choose to do it, get 5 pieces of 12" long wire in about 18 to 22 gauge. Your color choices are optional. If you have a 1995 to 1997 actuator (which I don't recommend the old ones unless you're going to rebuild them) you will need two additional 24" wires in the same gauge. These should be colored in a way that clearly says "ground" and "power" to you so you don't get confused later.

Now, for all actuators, use one piece of the 12" wire to join the wires on the actuator harness to the matching color wire on the head unit in the group you separated. There should be 5 wires in this color scheme:

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

The same wire colors should exist on both the servo and the head unit. If not, you've got something messed up, go back and check to be sure.

When all 5 wires are terminated/insulated at both ends, bind the whole bundle together to make a neat but flexible harness. For example, small spiral tubing, split loom, tape and tie wraps are all suitable methods and maybe you have more ideas.

If you have an older 1995-1997 actuator, you still have 2 wires on it you haven't joined. Splice the 24" pieces onto them. The GY/YE wire is the "hot" or 12 volt wire, and the black wire is the ground so use the appropriate wire color from the two wires you selected. DO use two different colors so you don't get confused when we connect them later.

You've now connected the actuator and it's ready to test, but lets get everything else wired first.

Fan speed controller

We're going to do a "temporary" job of hooking this part up. In addition to the parts, you need some kind of 12 volt lamp you can wire up. It could be a 12 volt test lamp, or whatever you like. We're going to watch it brighten and dim to show how the fan speed controller is working (or not working).

Whatever you use, make sure it doesn't draw more than a few amps, depending on what you will use as a power supply. You can test off your vehicles battery, but keep the load low for this. An old brake light, dome light something like that is ideal.

If you grouped teh "fan control" wires together, then you have these wires to work with. We'll use all of them except the YE/BK wire in this phase.

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)

Make a connection between the wires above (except YE/BK) and the matching color wires on the fan controller unit. Tape or otherwise temporarily insulate the connections so they can't short out.

There are two additional wires on the fan controller, larger ones (10 gauge) that we will be using as well.

OR/BK - "load" connection to fan
BK - ground, connects to chassis

Take the black wire from the fan controller and twist it in with the black "ground" wire from the head unit. If you have an old blend door actuator the ground wire from it should also be tied in here. These three wires spliced together temporarily are the connection where you will attach -12 volts from your power supply when you test.

The OR/BK wire from the fan controller goes to one wire on your test light, the other wire from your test light goes to +12 volts with other wires which will be described further down.

Okay, you've wired the fan controller. Now we wire the sensors in, set up the power wires for test, and we'll be ready to power up the unit! Isn't this exciting! I was psyched the first time I powered one up -- but hey, that's just me.

Sensor wiring

Each sensor has a pair of wires. On each sensor you have one PK/BK wire, and a wire of another color. They match these wires on the head unit. See the diagram below in the power wire section.

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

So, now just take the PK/BK wires from all three sensors and twist them together with the PK/BK from the controller head unit and tape them.

Then, match each remaining wire on a sensor to it's color match on the controller and twist and tape them as well.

Now the sensors are wired!

Power wiring

Now we connect together all the wires which will receive +12 volts. The sensor wires are also on this diagram.

On the head unit/controller you should have created this bundle of wires:

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)

Just take all the wires above EXCEPT the BK one (you finished the black wire earlier), and twist them together with the other wire from your test light. If you have an older actuator, connect the wire you extended from the GY/YE wire to this bundle as well.

Remember the WH/PU wire only is present on pre-1998 controllers.

Now you should have two wire points to connect, a ground (-12 volts) consisting of 2 to 3 wires, and a power (+12) consisting of 4 to 6 wires, depending on what equipment you salvaged. The RD wire is a line to control the display for either fahrenheit or celsius display. I have you connecting it to 12 volts (fahrenheit) -- but if your local units are customarily in celsius you may connect it to ground instead.

We're ready to test! (Insert drum roll here...) ;-)

Testing the EATC "offline"

Now we're going to connect power to this "mess" and see if it works. I know I said originally "test indoors"; but you can test out at your truck if you want.

Part of the reason for this phase of testing is to test the fan controller -- it's not tested by the more advanced self-tests we'll do later. Also, you can check for bad bulbs in the face illumination in this phase before you put it in your truck.

If you're going to test outside, then set the test-wired unit on a table near your truck and bring some kind of jumpers over from your battery. I recommend a 10 amp fuse in the +12 volt line between your truck and the unit to protect your equipment from catastropic shorts.

Inside or out, arrange the stuff so that there are no short circuits, so that you can see your test light, and so you can see the head unit display. Position the blend door servo with the shaft facing up so you can observe it's rotation.

Connect the ground first, then the +12 volts. The display on the head unit will briefly light up everything on the display, then go dark. This is normal initial power on testing.

At this point, you may see the shaft of the blend door actuator moving. It has a about 90 degrees or so of travel and it will hunt all the way to one extreme, then the other to test itself. If you don't see this happening, that's a bad sign.

You should NOT have your test light lit. If it is lit, you have either made an error in wiring, or your fan speed controller is defective. Verify your wiring before proceeding.

Now press the AUTOMATIC button on the head unit controller. The display should light up with a temperature (usually 65 degrees) and the word AUTO.

You may observe motion again on the blend door servo. Whether you do or not is not significant at this point.

After a few moments, your test light should begin to glow. It will probably go to full brightness slowly. As long as it's responding at all, that's good!

Next, use the wheel on the right hand side of the head unit to change the fan speed in "manual". The light should brighten and dim. If it does, your fan controller appears to be fine and you can use it.

Finally, if you want to, connect both the BL/RD and RD/BK wires to +12 volts. This will light up the buttons and you can see if all the bulbs work and arrange to replace them before installing.

If any are bad, you can carefully pry up the tabs holding the faceplate on to the main unit and pull the faceplate off and replace the bulbs. If you have the wrong color, carefully peel the silicone rubber caps off the old bulbs and install them on the new bulbs if you need to.

Advanced self-test mode

The EATC has an advanced self-diagnostic test mode. A great description of it can be found here on the P71 interceptor site I mentioned previously. What he's posted is a direct "cut and paste" from the Ford service manual. I'll paraphrase here and add some additional codes you may see not mentioned in that document.

Basically, what you do is press and hold the OFF button on the head unit, then press FLOOR while still holding down OFF. Now quickly release both buttons and press the AUTOMATIC button.

At this point a little line will appear to rotate in the middle of the display. This indicates testing is in progress.

The test can take what seems to be a long while when you're waiting for it! Just let it run and don't worry.

At the end, the display will begin flashing numbers, or it will simply light up everything on the display and halt.

If only "888" appears for the number, and everything else on the display is lit up, then you have passed the advanced self-test! Congratulations! You can now proceed with the installation.

If there are numbers, write them down as they appear. Here's what they mean:

022, 024 - Blend door actuator shorted

025 - Blend door actuator not responding properly

030 - cabin temp sensor shorted (either wiring or bad sensor)

031 - cabin temp sensor not connected or failed (open circuit)

040, 042 - outside (ambient) sensor shorted (wiring or bad sensor)

041, 043 - outside (ambient) sensor not connected or failed (open circuit)

050, 052 - solar radiation sensor shorted

115, 125 - bad/no data from vehicle network (you'll get this always testing outside the vehicle)

There may be others depending on the year, particularly network ones -- but these are the main ones you have to deal with.

Whatever happens, press the DEFROST button to clear the codes, then activate self test again.

If you got numbers, they may be the same ones, or some may be missing. Sometimes the first self-test is misleading which is why we're doing it again.

Based on the numbers, troubleshoot your wiring and sensors.

If all you get are 1xx codes, and your fan controller worked in the first tests, then you are good to go! You can proceed to the next phase -- installation!

Press DEFROST to clear the codes, disconnect the power, and unhook all your temporary connections. If you had problems, get them fixed and try again!