This reminds me of an anecdote years by my lecturer back in NUS.
-A man's home window unit (air conditioner) is not cooling his room well. He ask his friend, who happens to be a A/Prof in Eng - aircon included. This friend immediately took a piece of paper and draw the P-H diagram (Mech. Engr will know what it is) to try to find out what wrong -.
My lecturer said it was a true episode. He said he found nothing wrong with the approach technically except..... And I am very sure that man solve his problem from somebody else.