This business is tough without the added stress of friends who aren't quite sure what they want or if they can have it done cheaper.
Sometime back, a friend purchased a used water well rig, which had a new compressor installed prior to his purchase. The rig was a few years old, so he began to tell me details of why the original compressor was replaced, and most important to me, why he had called me after years of not hearing from him. Case in point: after a couple hours of water well drilling, the rig engine would drop a couple hundred rpms, then without notice, the engine would shutdown. As I took down the information, while talking to the customer, my service partner made a quick inspection of the electrical safety shutdown system.