I had the same issue with my vent selector. When I bought mine it barely moved and after pulling the center console I found the cable housing had popped out of it's retaining clamp. That stopped the cable itself from moving within housing and instead the whole cable moved. I was able to loosen the screw for the retaining clamp, slide the housing back into place and tighten it down. While I was in there I did lube up the slide surfaces.
It just happened again this year, but I think because my easypass holder dropped one of it's three suction cups down the defrost vent. When I went to slide to defrost, I felt a little resistance then a pop sound. Now it feels the same as when I bought it, so I'm going back in to fix it.

Thank you guys, if I get time this weekend I'll do some digging. <img src="/forums/images/graemlins/kewl.gif" alt="" /> If y'all never hear from me again I blew something up while I was in there <img src="/forums/images/graemlins/notooth.gif" alt="" /> WHile looking under the glovebox area I noticed what looked like a plug hanging out with nothing plugged into it, but of course I don't have a digital to post pix up. I'll work on that one, too...thanks again.
This forum rules.

I don't have my FSM to check, (my folks are visiting for the holidays and snoring up a storm in the room the manual is in, LOL) but I believe there's a test connector in that area. Not supposed to have anything connected to it.

This is the "mystery plug" on what I'm assuming is the ECU.

Here's the fuses right off the + battery post, everything seems tightly connected to this and it isn't real corroded or anything. THe whole time I was checking this out I was expecting to end up like this <img src="/forums/images/graemlins/zombie.gif" alt="" />

this is the other end of the heater control stuff, right? THat lever seems to move, but the switch (actually the one that adjusts fresh air or recirculated air) doesn't want to.

and last but not least, thanks to you guys I finally reset the switch thingy so the MAINT REQD light is off. THis is a shot looking thru the window at the back of the instrument cluster after I disconnected the door buzzer thing to the right of the photo, the hemostat is pointing right at the switch. Just in case anybody needed a picture of that.

I think it is the body/engine grounds gone wild ! Clean or replace them, and check volt drop at the same time
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Are there a lot of grounds, or is it just a couple? WHereabouts are they located?

Now I'm real motivated to fix my Monty issues because this just happened to our other car: <img src="/forums/images/graemlins/angry.gif" alt="" />

THank you everyone for all your advice.

Your mystery plug is the diag connector. That's about all I can help you with. Other than, like everybody else said, clean all your connections and verify grounds.

Check your connections as the others have mentioned.Check battery cable where they attach to the battery.Then follow the ground wire to where it connects to the frame and then the engine block. Look for rusty/corroded connections. Then follow the +(positive side) battery cables looking for corroded connections also.

Are you sure the alternator is charging correctly? Please check the grey terminal block shown in the 2nd picture you posted(the one with the red and green colored jumpers) they are fuse links.They feed power to lights and other circuits. Had similar problem with lights failing to work at times, the terminals were corroded at the fuse links. Do you have voltage meter and can use it? If so it will aid you greatly.

The key to finding your trouble is finding the common thread. You are having light(both interior and exterior) and engine electrical issues. Therefore you probably have a battery/bad ground/alternator/main power distribution problem. Ask and maybe someone can send you a link or a email you the pages from a FSM for your year/model with wiring diagram. For these types of problems the wiring diagram is you best friend
Good luck......hope this helps