The "Thermo Control Amp" likes to go bad, but I'm pretty sure when that fails the AC completely stops cooling - it sounds like yours is kinda working.

Anyway, you might want to search old threads for the TCA just to learn about it.

I've only ever had two AC problems in my '00 - the TCA went bad, (fortunately that was like a $40 do-it-yourself fix) and one of my freon hoses split.