This group of 31 lessons average 15 minutes each plus a short quiz. The intent of these lessons is not to show you specific nuts and bolts of a single design, as YouTube often does, but to explain what they all have in common so that you will soon be able to diagnose all models. Following are two very short samples to acquaint you with the style of presentation:
The first comes from the lesson on range temperature control systems both old and modern.
The second sample is from the lesson on understanding the basic principles of refrigeration.