The answer is probably not just a filter. There was an issue with the AC Control Module for the Protege5 that was not actually fixed until cars that were produced after Dec 2, 2002. Common traits for this are, the AC will work fine on some settings, but light will go off and, although fan is blowing, stops being cold on some settings. This will progress to where the light will not come on for some fan speeds at all, and progress through the different speeds. Google for 02 Protege5 air conditioner and look at some of the blogs. Lots of info for possible fixes outside spending $500 to having it replaced.