[LoneStarSoldier]

The other day I turned on my A/C and a terrible noice came from under the dash....Sounded like door had closed in the vent system, never heard it before....Is it something that needs repaired.....El Camino is an 86....
Have a Great Day!!!!!!!!

 

[87next2last1]

Maybe the blend door was stuck & then It slammed open or closed ?:dontknow:

 

[darbysan]

The door that moves the air from the floor and defrost to the dash sometimes gets stuck, and will open with a thunk once the vacuum overcomes the stickiness of the gasket. Might be what you heard. No worries, unless you don't get the air out the vent like you expect. Then you will need to check vacuum lines, etc.