I JUST had my water pump replaced and all was well until today...

I have a 1996 C280. Recently if I have the A/C on when I start the car and attempt to drive the car stutters a little and you have to start giving it some gas to get it to stop, it stops after running a while.

Today the A/C vents made a funny noise, like the opening and closing noise when you first turn it on. Sort of makes a hissing sound.

This isn't present when on defrost or heat, only when programmed for cold air. The air is no longer cold and the sound persists.

Could this be a condenser issue? Freon? or is it something else, maybe a fan or belt out of vacum leak?

I am not very knowledgable when it comes to cooling systems so any help will be greatly appreciated. Its hard to drive a car with no A/C in 100 degree Dallas heat.

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2004 CLK500
2000 S500