EATC self test?

Deathacus

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I've been having trouble with the blower on my '94. I tried to run the self diagnostic (Floor/Off--Auto)
When I do, the screen stays blank for ~10-20 sec, and then the entire display lights up, everything! (see below). Is it supposed to do this?
Not sure if it means code "888" or if its just freaking the heck out.
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NoSlo

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"After about 20 seconds, a code will appear in the window"

"If no DTCs are generated as a result of the self-diagnostic test (888 code is displayed), determine the symptom and go to the symptom chart"

Since the blowers are a moving part, and have brushes that can wear out, that is the most likely fault. A lo mile wrecking yard Taurus might be a better bet than a new motor (which are also cheap), because getting the plastic fan impeller off the shaft requires force that makes you think you are going to break it.
 

Deathacus

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Hi NoSlo!

Thanks for the input! My blower actually works fine--on high--hence why I think it's the resistor/speed control.
As for the code, I took a look at the service book, and according to it a blank screen is supposed to be no code. "888" is:
  • Temperature control lockout valve and switch inoperative.
  • Vacuum system inoperative.
  • A/C clutch inoperative or damaged
I just don't know if it really is a code or if the whole unit is malfunctioning, I wouldn't think everything else on the display is supposed to light up like that.
 

NoSlo

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I see that you have a an old broken button EATC instead of a hard button 95 or further upgrade. For 95, the service manual indicates exactly what I typed. For 1994, 888 code displayed are indeed what you list. You can see if the EATC has frozen: press the blue cold temperature button and it should exit the test, which is also the normal procedure before key-off when in the test.

The blower motor speed controller for AC with EATC is not listed on the parts sites. It will have a part number similar to XXXX-19E624-XX. For one listed as compatible with only G3 and after, YF3Z-19E624-A.

The blower motor speed controller will be similar to 1994 Thunderbird's FOUR SEASONS 20372 for $250+ - which uses a pigtail adapter. In 1994 Taurus, wiring is +12: Light blue/pink;
ground: black;
from EATC: tan/orange;
to blower motor: orange/red.

One T-bird owner reports a blown transistor and this symptom, so component-level repair may be possible if you can't find an EATC Taurus or Sable at a wrecker. It's located in the fan's blower housing.

You can see that replacing the $20 motor with a refreshed one is the place to start. Mine was intermittent until I got around to replacing it.

If you want an unbroken EATC, I have a box of them in various states of "bubble button" modification.
 
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Deathacus

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Thanks! I pulled the plastic panel under the dash earlier and couldn't even find the part, this will help a lot!

And since you brought up the "bubble button", is there any advantage to that vs. a '95 unit?
 

NoSlo

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Thanks! I pulled the plastic panel under the dash earlier and couldn't even find the part, this will help a lot!

And since you brought up the "bubble button", is there any advantage to that vs. a '95 unit?
Just in appearance

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This one modded with blue plastic for the VFD, and blue LED button illumination.

Also, when 888=vacuum system inoperative; did you have the engine running?
 
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tracy_s_1993_atx

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Here is photo of the variable speed controller module.
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When my variable controller failed, the fan was always on high.
I tried to find a replacement transistor but no one could cross reference the Motorola part number. I called Ford and Motorola.

You can get these controllers new on ebay, but be prepared to spend a slight fortune.

Michael
 

NoSlo

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Same fault: 19 years ago on the forum

 

luigisho

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BCM sounds right if it's always stuck on high. I haven't had to replace one in a long time but is a frequent failure part over the years as I recall.
 

tracy_s_1993_atx

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I may have found a suitable replacement transistor for the variable speed fan module.
I need to make a diagram and see if the transistor is a NPN or PNP.

Michael
 

tracy_s_1993_atx

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I believe that the PowerBase power transistors on the original Ford variable speed controllers are either 2N3773 or 2N6609. That is just for reference if anyone else wants to attempt to repair the variable speed blower module.

I will post a schematic when I get a chance.

Michael
 

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