I get called into a lot of jobs when the "trained technicians" can't get a it right. I walk into shops that have a lot of "wall paper" all these certificates of all the training that their techs have been through. But if the problem is just slightly out of the normal realm they can't diagnose it. I just got called in on a brand new boat. The bow thruster would only turn in one direction. They replaced the unit, they replaced controls they "checked" all the wiring to no avail. Time to call "Expensive Ed". One look at it I turn around and tell them "The cables are too skinny". I calculated the load to line loss and told them to replace the 2/0 cables with some 4/0 ones.
Got a call a week later everything was great. Then the shop chief said he knew I was a diesel tech but he didn't know I was an electrician too. I told him I'm not an electrician . But any good diesel technician needs to know electrical theory. If a diesel tech can't figure out battery cable size how can he properly install an engine. Under size the cable and you will have all kinds of starting problems. A lot of "qualified techs" out there have no idea of basic electrical, hydraulic and mechanical theory. Also they have no process of elimination skills so they can't diagnose real problems.