How long should a car hold vacuum after being turned off?

[RustyDusty]

How long should my system be able to hold vacuum for after the engine is turned off?

 

[Mrmopartech]

Are we talking about the A/C system or the booster,as you are not clearly stating what your problem is or if you are sure what is normal or not,mrmopartech

 

[RustyDusty]

Sorry, the AC system. It holds a vacuum for only about 30 seconds after the car is off, then it defaults to defrost.

 

[440Ken]

Sound like a bad check valve.

 

[RustyDusty]

That's what I thought. I checked the check valve by blowing/sucking. Must be a cracked hose.