Diagnosing a HVAC vacuum issue on a Ford F53
The AC/heat is switching to the defroster under higher RPM conditions on my 2006 F53 chassis Damon. It actually seems to be doing it now under low throttle steady state conditions as well. Obviously...
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JaxDad wrote:
Take a small propane torch and unscrew the head leaving just the valve and pipe, then slip a piece of tubing over the end of the pipe. With the engine idling and the valve on the torch open (but not lit obviously) run the end of tube along every vacuum tube in the HVC system.
When you get to the vacuum leak the engine will inhale the propane and the extra ‘fuel’ will cause the engine to speed up a little, when you pull it away it goes back down again.
It makes finding vacuum leaks super easy.
I've been around the auto repair industry over 55 years and just learned another trick to add to my repertoire. Thanks for posting.
With this trick, I'll bet even Doug will consider looking for leaks.
Richard
