2000 GC Rear Vent intermittent

My 2000 GC passenger side rear vent opens very intermittently. It ALWAYS closes, but opens only when it wants to. Driver side ok. What should I check and how do I check it? Thanks for input!

Try pushing on it from the inside when you try opening it. If it opens, you likely have a weak motor that needs to be replaced or less likely, the linkage is bound up. If it doesn't open the switch could be the culprit but, could still be the motor. Can you use a meter?