AC blows thru vent, then thru defrost????

[stangeater]

Just like the title says. My AC works great (as far as cooling goes), but when I have the climate control on MAX AC, it wants to switch back and forth between blowing out the vents, and blowing out the defrost vents. It blows for like 15 seconds on one, then switches to the other, then back.........Any ideas what causes this? Thanks!

 

[matasho]

no idea but my heat does this also. any one know what causes it?

 

[shoclown]

you have a vacuum problem...i would bet that the storage tank under the fender well is cracked ...when the vaccum is lost it defaults to defrost so it loses vacuum goes to defrost then recovers switching but then its not enough to hold so back and forth...it could also be a one way check valve for the vacuum storage allowing what is in there to leak out...i would check both the check valve is within a foot from the storage tank in the line that goes on the tank..good luck

 

[stangeater]

you have a vacuum problem...i would bet that the storage tank under the fender well is cracked ...when the vaccum is lost it defaults to defrost so it loses vacuum goes to defrost then recovers switching but then its not enough to hold so back and forth...it could also be a one way check valve for the vacuum storage allowing what is in there to leak out...i would check both the check valve is within a foot from the storage tank in the line that goes on the tank..good luck

Where exactly is this storage tank under the fender well? On the passengers side I'm guessing? What does it look like? Thanks for the info!

 

[matasho]

damn i had that thing off a few years ago when i had the front end off for painting. mine has done since that winter when it got cold and i started using the heat again. bet i didnt hook up the hose good enough. but thats good news i thought something was wrong with my climate control head unit. il check that out......some day