GPBrim
New Member
I had searched the forum and came up with numerous ideas and suggestions from all of you, as always thank you, but I have found that the defrost only can be caused from a the vacum switching module that the vacum lines plug in to at the back of EATC unit. You can take two screws out of the back of the unit and pop the black cover off the top and that will reveal the switching unit for the vacum source that controls the rest of the heat controls as far as defrost, vents and floor. I ran the usual diagnostic and got no codes whether this piece was plugged in or not. I grabbed my vacum gauge and found that I had 20 inches of vacum in the car which matched the vacum at the intake as well, I also used a piece of hose and jumpered the black vacum line with the yellow that controls the area that you want to put the air through, ie. Defrost, Vent, or Floor and it switched over with vacum applied to the yellow line. So with the cracked vacum line theory laid to rest, I went to one of our local pick and pull junk yards and got another one. Unit is easy to replace as it is a plug inside the EATC unit and the vacum lines to completely remove it. Just another thought for some of you who might be having this same problem. Hopefully this has not been gone over already as I couldn't find anything about it via search here. Hope this helps, if there are any questions that I might be able to answer, feel free to hit me up, always glad to repay the members here who have helped so many others! Thanks all,
Gregg
Gregg
