Crypto - I replaced mine in a 2000 about a month ago. I had similar thoughts where sometimes it seemed to be working but then I did finally hear some clicks when moving my temps from hot to cold. That was the best sign for me along with the cold air. I did my heater core a few years ago so I was figuring that was not my problem. I would cycle the controls and listen closely. I replaced mine in less than an hour so I would not hesitate to do the job yourself. Just be sure to buy the $5 tool to pull the radio as it makes it go very smooth. Good luck!