Since you have a basement a/c, there is no left/right a/c. But if you are talking about the vents in the ceiling, and you're not getting much air flow from the drivers side, then the problem is probably a major leak in the duct work in the rear of the coach. There is a big "Y" that splits the air to driver and passenger side.
One member "FIRE UP" has a good photo of what the venting looks like with the rear cap off on a coach like yours. Here's a thread with the pics:
http://www.irv2.com/forums/f101/base...em-309312.html
Here's a link where you can download a the removal procedure I wrote many years ago. It makes it pretty straight forward to pull the Basement A/C if you need to get at it in the future.
https://docs.google.com/viewer?a=v&p...zBiZTYxYzU5ZWQ
Here's a link to the Coleman RVP Service manual:
https://docs.google.com/viewer?a=v&p...GI4N2U4N2MzODE