Troubleshooting tip: Dynon D120 EMS sensors are closely tied together

[Anticept]

Putting this out there. While changing to an EarthX battery for my CTLS, I thought I had fried my EMS unit when I dropped my wrench across the battery terminal and right EGT. (This is what I get for not following my rule of ALWAYS disconnecting the negative battery terminal, and reconnect ONLY when electrical maintenance is complete)

The result? Not only was my oil pressure reading "---", but my EGTs were reading -99, and voltage was lower than normal. I pulled the unit in defeat and was getting ready to send it in for service, when I asked another CTLS owner if I could just plug it in for a moment to really verify. Imagine the surprised but relieved look on my face when everything read normal.

So I go back and plug it back into my aircraft, and still reads abnormal. So I figured maybe I broke a wire by mistake. Started from the oil pressure sensor since that I need to have working for flight, and I found the ground wire used to hook up the 200 ohm resistor going to the ground wire to my oil pressure sensor (a retrofitted piezoelectric type). To verify operation, I started the aircraft with wire in hand, touched to ground, and ALL of my instrumentation came back to life.

So apparently, the instrumentation in the Dynon units are closely tied together and not very well isolated, so a malfunction in one sensor may very well be affecting readings in others. So it's important to keep your sensors working properly.