Monday, January 23, 2012

AC air blows through defrost vent only on Ford F-350 6.0 Diesel Engine?

Its a vacuum related issue.Noticed by many other care drivers too.

This is how your system works :----
Inside the dash there are vacuum operated motors that move doors in the dash to control air flow,the vacuum motors use vacuum to control them ,to open and close them.When the system has NO vacuum then it faults to defrost.So the problem is that you have no vacuum to the motors in the dash

Since you have a Diesel engine ,, it does NOT make vacuum like a GAS engine does, so a Diesel has an electric vacuum motor located under the hood by the right side fender

See the diagram below for better understanding:----

So check if this vacuum motor is working .For that turn the key on but do NOT start the truck,if you hear the vacuum motor running and will not stop running then you have a vacuum leak some where.
But if you do not hear the vacuum motor run,then pull off the vacuum hose on it.
If it does not run when you pull off the hose,then there is a two wire conector to it ,you should have power on one wire and ground on the other, if you have both ,,,then the vacuum motor is bad and needs to be replaced.

This detailed instructions will help you.


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