This is for a 1980 300SD. My daughters normally drive this car and they happened to tell me the other day that the A/C was not working. So, I started driving it. It seems like it is trying to cool. If it is hot out, there is just a hint of cool air. If it is cooler, like in the morning, it just about froze me out. So I am thinking that the valves quit working or is stuck open or I have a vacuum leak. I know the whole system can be a nightmare and I can end up taking half the car apart. Are there any hints or tricks that could help me track this down. Or even most likely part to go after. Given the above I am cancelling out the servo or the ampliphier, even though I have back up parts for these. Should I change them anyway?

Have the pressures checked to see if there is enough freon in it. On cool days an air conditioner can freeze you out so to speak and still be low on freon.