oil pressure and water temp gauges

[Michael Pliska]

Originally Posted by jim hensley

just a comment on gauges. a couple of years ago, I was intrigued by the digital gauges, and I installed a pair of water temp, oil pressure digital electric gauges in my car. they would read fine when the car was idling, but once power was applied, the gauges would go crazy, flickering very fast so you could not read them. I contacted the manufacture and they had no idea what the problem was. I suspected a grounding issue, but rather than fool with it, I put the mechanical gauges back on and problem solved. Still curious what it could have been.

I would just about guarantee it was electromagnetic interference from the car's ignition system, scrambling the microprocessor in the gauge. It takes some design "tricks" to avoid susceptibility to EMI.