So you are saying if you have vacuum to the actuator it won’t pull in but if you push it in, it will stay in? If so the actuator may be bad but make sure the door moves easily by disconnecting the actuator & working the plastic arm by hand. If it doesn’t move freely, there may be something inside the box interfering with the door movement. Use the link below to see how to remove the actuator. Since you have a 2001 you will have to use either the ’00 or ’02. The procedure is the same but the locations are different. Use the one that looks like what you have, probably the ’00. Go to the heating & A/C chapter (& controls section for ’02) & towards the end there will be what you need including a drawing of the actuator being removed.
See online read only FSMs here:
Jeep Knowledge Base
You may have to go to the bottom of the page & pick Jeep Resources & online manuals if it directs you to home page rather than the knowledge base.
Pick your model & year then on the drop down menu pick the chapter you need.