97' Blazer 145k miles. This system was charged a year ago, now it's blowing warm air, along with my 2 other cars, 95 Grand Am, and a 90'Pontiac 6000which were charged last year as well. I just want to know is there a common thing that goes out? Is the pump the most likely part to go out {leak}first? Especially when there is a green residue on the pump.Thanks.

 

Usually green residue is a sign of leaking. Usually, no part is more likely to leak than another. However, if I were to pick one it would be the condensor. Because the condensor is at the front of the car, it is most likely to get hit with a rock or other debris on the road and start to leak. The best explination for your problem, just by looking at the age of the cars would be climate change. Over the winters, o-rings at the hose ends contract and expand in the engine compartment with temperature change from a cold to hot engine. The added stress on the old o-rings will cause them to crack and most often and leak with age. However, before going to get the cars serviced, there are a few things you can check before that may cause the same effects as a depressurized a/c system. Check the condensor and make sure its not blocked with dust and dirt. Also a good one I came across on one of my trucks the other day was the cold/hot air control in the car. If you move the **** from cold to hot in the car, make sure the door in the ducts move, otherwise it may always be directed over your heater rad all the time. Hope this helps a bit.