hi i have a 2000 ford windstar for a backup car and i needed it this week and the ac does not work. now it workes fine last summer but sat all fall,winter and all of spring without running. 3.8 liter v6 100,000 miles. the compressor just kicks on and off about every 10 seconds but no cold air what could be the problem? i have put about 200 miles on it this week so i know it is fully warmed up.