The A/C blows cool (not cold air as before)& will not cool the car on a sunny day, no matter how long a drive. I hear a click when A/C is turned on, blower works, radiator fan cycles on if left to idle with A/C on. No new or unusual noises. Low pressure line is (not terribly) cold, high pressure is slightly warm. I can't see any signs of leaks. Can I just recharge, or is there a larger underlying problem?