Speaking for the people that two years from now that have to figure out why your product suddenly stopped working, you should never rely on soldermask for insulation (been there done that). Or are you giving someone else an opportunity for a future 'Sherlock Ohms' submission.
On a tangent; I once was asked to help when a car would not shift out of Park when the brake pedal was pressed. And also, the brake lights were not lighting when the brake pedal was pressed. It turned out to be a loose wire at the switch. The brake lights turned out to be a troubleshooting test.
Isn't that always the case-? Diagnostics taking longer than the corrective action-? Makes me think of a recent issue I had on the product I was designing. I had hand-assembled the very first (10) working prototypes, but every time I tightened down the outer housing screws, the display blanked-out. I spent literally 2 solid weeks of assembly evaluations and diagnostic trouble shooting before I narrowed the cause to the lack of insulated solder-resist on the PCB top layer. Tightening the housing screws simply squeezed the metal modem casing onto exposed circuitry which should have been insulated during the PCB fabrication process. Corrective action was a 1c piece of Kapton tape under the module. Two week investigation; 10 second fix. Of course that is a natural part of development and this type of issue must be completely resolved months before production. I hate to see silly issues like this affect the consumer end-user.
John, I will bet you that the time you spent diagnosing the problem was longer than the time you spent fixing it. This is the problem with many automotive systems. With the advent of very inexpensive microcontrollers, this should be the next wave of automotive improvements.
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