EATC defaulting air flow to defroster question

xtriggerman

Registered
I'm finally getting around to fixing all the small issues on this 97 and this one needs seasoned in put. I have the shop manual with the extensive trouble shooting procedures but there is an issue the manual does not address. Every thing works and lights up as it should aside from the air flow is in the default as in defroster vent only no mater what you push. I can't get the EATC to go into self test! I tried a dozen times.... push OFF and FLOOR together and in 2 seconds push Automatic. Nothing happens in the window aside from what ever was going on before the 2 button push. When I start the car, it looks like all the LED characters light up in that split second but no way can I initiate the self test to see if there are any DTC's. I had read some where that these things can go into default simply because of a battery disconnect and you can restore the air flow registers by simply clearing any DTC codes. Is this a indication that the module is shot? Any ideas? This car only has 69K miles on it.
 
The EATC defaulting to defrost only is indicative of a lack of vacuum to the EATC controller.

Vacumn1.jpg

Vacumn2.jpg
 
Thank You for your response and that second diagram is most informative. Looks like I'll just go ahead and start the trouble shooting procedure as out lined in the shop manual. As you have mentioned, it starts out testing from the vacuum manifold port and works its way back. Still odd that the EATC is not responding to self test start up. You would think it wouldn't need vacuum to initiate but stranger designs are out there!
 
Well, it ended up being the EATC module. The used one I bought off Ebay fixed the problem all tho even this "good" one will not respond to the self test input. Whatever.... Boy this Lincoln sure can move air out of the dash vents! Very happy with it!
 
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