EATC self test?

[Deathacus]

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.

 

[NoSlo]

"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]

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]

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.

 

[Deathacus]

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]

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


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?

 

[tracy_s_1993_atx]

Here is photo of the variable speed controller module.


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

 

[Deathacus]

Tried with and without the engine, cool, warm, sunny, night, driving, idle, all the same

 

[NoSlo]

Same fault: 19 years ago on the forum

blower has just one speed......

....full afterburner. My 93 SHO, the entire 3 weeks I've owned it seems to have a on off switch for the climate control motor. Push it to the off position and it's off. As I start to push it towards hi, it stays off and then, all of a sudden as it is at about 80-90% throttle, BAM, it comes on...

shoforum.com

 

[luigisho]

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]

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]

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

 

[Pdr1966]

IS anyone still looking at this post? Have a 94' same problem.
Looking into doing a component/transistor repair

 

[SHOrod]

I don't think I still have my old, faulty, EATC blower motor speed control module to do some tests with. But if you have access to an oscilloscope, you should be able to confirm what frequency and amplitude the PWM is as well as whether you need an NPN, PNP, or possibly even a FET (although that was not very common in a TO-3 case). I might still have a DATC module sitting around from my former Lincoln LS. I'd suspect that PWM signal is quite similar to what was used in the 1994 Taurus.

-Rod

 

[SHOrod]

After looking at the factory wiring diagram for the blower motor circuit I can say with pretty high confidence that the transistor will be an N-channel. Not sure whether BJT or FET. If you're able to open your controller up enough to sketch out the schematic we may be able to determine FET or BJT, and since we know the current capacity of the circuit, we should be able to select a reasonably good candidate to replace the house part number transistor Ford used.

-Rod