I just wanted to find out the common things that break on a service call. So I can pay some extra attention to them while I'm in classes. In the beginning classes everything is running and we mainly do the activity that is in the lab manual. Like checking our superheat and sub cooling under different loads, charging/recovery/evacuating or wiring the compressor. My best guess is that anything that is moving like the compressor, contactors, fan motor. I'm also thinking that some parts are really expensive to replace. The reason I'm asking is that these next 3 days we have a open lab before class ends and I just wanted to get familiar with what I am mostly likely to find out in the field.