I just bought a 91 Civic LX and I have a problem with the air conditioner. It will run for about 10 minutes and then won't cool for 30 minutes or more. It has plenty of freon and the pressures are ok when compressor is running. Has anyone else ever had such a problem and figured out what it was. Also my windshield wipers are making a knocking sound occasionally. Is the noise caused by the motor or something in the linkages that wear out?