The KISS method works most of the time when the failed component is the cause of the failure. KISS method doesn't apply to electrical because a simple solution is normally part of a complex problem. The KISS method of electrical is you have to understand and work the system, and you can't jump into the middle and swim your way out most of the time.So many 'mechanics' (paid or shade tree) ignore the KISS principle - jump to conclusions without observing and testing adequately. I worked on my own motorcycles for many years and small engines as needed. Probably 95% or more of the problems are the easiest, simplest, cheapest thing to fix but you have to understand each system and how they interact as part of the whole.
Just had another service center call me the other day. He was working on a Toro Z turn and had lost the ground to the solenoid, hour meter, pto, and fuel solenoid on the Kohler engine. If he jumped the solenoid the engine would crank but not start. Basically he had lost the frame ground. Which seems odd considering the frame ground would grounded through the engine with the ground wire attached to the engine. So while we talked on the phone I pulled up a wiring schematic so I could see were everything went. And started tracing ground circuits, and found that everything in question terminated at a relay. He said it clicks when the key is turned on so appears to be working. Asked if they could be tested and I said yes, but would need both a 12v battery source and a meter to properly check function. He said I have a spare relay I will just plug it in a see what happens. Immediately everything started working. But without a working understanding of electrical systems and the schematic would of been a parts cannon scenario.