heater switched from vent to defrost after shifting into 5th

[chris71]

this has never happened before as i was driving home from work last night . i had the heater on vent when shifting into 5th gear the heater switched to defrost for a couple minutes? i've never noticed this before also i haven't had time to look at till tuesday when i'm off work , i'm thinking it prolly a vac problem but not sure . so i'm wondering if anyone has had this issue before and maybe a place to look and see where the vac leak may be at. any advise would be nice to narrow down where to look . i'll have the dash apart tuesday to change the gauge cluster from idiot lights to gauges , so i'll be able to check the vac lines in the dash at the same time 

 

thanks, chris

    

[shelbyluvv]

There is a vacuum ball behind the passenger side front bumper. Check there and look the line over very well all the way to the intake.

[chris71]

thanks i'll check 

[bodukexj]

Classic vacuum problem. Check, check and recheck the vacuum lines. I usually just run a direct line from the manifold to the heater control panel. (It's a safety thing; all vehicles are set up to failsafe to defroster if they loose vacuum- you don't need cabin heat, but you do need a clear windshield!)

[cruiser54]