Grounding on OAT/EFIS-D10A/EDC-D10A harness

[Varso]

Originally, my EFIS was detecting and reading the remote compass ok but lately the compass was stock to a compass reading regardless of the airplane's direction.  I assumed it was a bad connection and decided to redo the wiring.  I noticed that the ground wires to the DB9 were soldered together and  connected to pins 1 & 8 of the DB9.  I decided to clean the ground connections by connecting the OAT ground to pin 8 (blue) and the EFIS ground to pin 1 (white).  Now the EFIS does not find the remote compass anymore.

I recall reading that at one point, the grounds were soldered together but I also recall reading it was not required.  Could someone confirmed what is the right way to ground the OAT/EFIS/EDC?

EFIS-D10A SN 5745 Firmware V5.5
EDC-D10A  SN 9071 Firmware V?.? but probably at 4.04

Thanks

Francois

 

[Dynon]

Pins 1 and 8 are both grounds on the EDC-D10A. So generally, pin 1 goes back to SkyView, and pin 8 is available for you to connect the OAT's blue wire to, giving it its ground path. But basically, as long as all of those things are ending up shorted, it doesn't matter. Actually, it took a few years after the EDC-D10A's release for us to remember that we had made pin 8 available as a ground. So older installations have both the EDC-EFIS ground and the OAT blue wire spliced into pin 1. So either way has been "right" at some point, and it sounds like you've wired it one of the correct ways.

The difference in firmware version difference between 4.x and 5.x isn't going to be the culprit here. Though we generically say they should be the same, in reality the EDC firmware didn't materially change for a while, and anything newer than (don't quote me, even though I'm writing it down) 3.x and higher are cross-compatible between the EFIS and EDC.

The fact that your heading was misbehaving in the way you describe is a clue that the EDC might be having a more fundamental issue though. I'd make sure all four of the primary wires that are going between the EDC and EFIS are pinned out correctly and still and have continuity from end to end, especially since you were changing the wiring.

 

[Varso]

Thank you for your quick reply and for clarifying the ground connections , I will recheck my cable with a ohmmeter.

Just another quick question.

Does the metal shielding need to be grounded to the EDC and EFIS casings?

 

[Dynon]

Shields should get connected to ground at one end but not both.