Heat Only From Defrost

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bigshow1122

Registered
Here we go with the first authentic post for a question. I have a 93 Mark VIII and that is only putting heat to the defrost. I have been told that this is a safety precaution when something else isn't working right. No matter what button I hit on the ECM it always comes out of the dash....Have any ideas? I am assuming it might be a vacuum leak? Do you guys know of any tips or (first thoughts) that I would check before really getting down and dirty with this scavenger hunt?:p
 
It is a vacuum leak. You'll have to go through the vacuum lines and find it unfortunatly. Check some connectors on top of the engine they tend to crack with age... especially the rubber pieces.
 
Figures

Figures

Yeah, that is what I was afraid of.....Was praying it was a fuse or something like that. I know if its anything like a lexus, there was a fuse on there that controlled a small solenoid that allowed the airflow to switch but I didn't think I would get that lucky again. Off to the garage I go!
 
Yes, defrost mode is the 'default' vacuum position of the heating/cooling selections.
 
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