1998 Honda Civic A/C Blows Cold then Hot

The very 1st thing you need to do is make sure system has the proper amount of freon. If it is low, a/c will cycle on & off, if it is overfilled it can do this also. Depressing shrader valve to see if freon comes out does not tell you how much in system. If you can't afford to take to shop, you can purchase freon @ auto parts store & shoot some in in case it's low & see if it straightens out. But if it's too full, this can damage a/c components like compressor which can turn into big bucks. The very best thing you can do is have it connected to a A/C machine somewhere & go from there, this way you won't make problem worse. Good Luck.