I visited a friend in the bayarrhia. His business neighbor was an auto shop. One day the owner came to me and said "I hear you are a troubleshooter". A poor customer had paid over 500-dollars for various parts to stop the A/C from cutting out when the gas pedal was depressed. The idiot had several junk cars parked out back. I spent 3-minutes locating a heater control inline vacuum non return fitting. Problem went away.
Decades before I was southbound on I-5 with my Caddie. Shut it off in a gas station. Would not crank because of classic GM starter motor heat-soak. Pimple-faced kid runs out with his cheese grater load tester. "It's your alternator" he pronounces...
"Sonny, wanna know what I do for a living?"
He vanishes. I get into the car and drive off.
It's no joke. The aptitude or honesty in the repair trade is a disgrace.