VAF Forums

VAF Forums (https://vansairforce.net/community/index.php)
-   RV General Discussion/News (https://vansairforce.net/community/forumdisplay.php?f=2)
-   -   First start- no start. (https://vansairforce.net/community/showthread.php?t=147517)

rvbuilder2002 03-13-2017 01:01 PM

Quote:

Originally Posted by Tommycat (Post 1157414)
.But it seems to me that the most recommend one is the return ground thru wire shield. As per this diagram...

I'm not one pf those people.....
The long term durability of the P lead shield is vulnerable depending on how it is actually completed (There is strong evidence that first time builders don't always have a good idea what to do here). This then makes it highly likely that at some point in the future the airplane will have an unsafe mag because of a failed grounding path. It is for this reason that I promote sheild connection at one end only and then use an airframe connection to the switch ground as the grounding source.

None of this is relevant to the O.P.'s problem though because the ground is used to disable the mag, not enable it.
Even if the ground it hooked up incorrectly, as long as each P lead is connected to the switch properly, the mags should fire the plugs (but it may cause an unsafe condition by not disabling the mags when the ignition is off).

deek 03-13-2017 02:22 PM

[quote=rvbuilder2002;1157468]I'm not one pf those people.....
The long term durability of the P lead shield is vulnerable depending on how it is actually completed (There is strong evidence that first time builders don't always have a good idea what to do here). This then makes it highly likely that at some point in the future the airplane will have an unsafe mag because of a failed grounding path. It is for this reason that I promote shield connection at one end only and then use an airframe connection to the switch ground as the grounding source./QUOTE]

^^^ I live in this camp too. 5 EXB, all wired this way, 7,000+ trouble free hours.

Dave Bernard 03-13-2017 06:46 PM

Well guys this whole process has been humbling, educational and now embarrassing.

This whole thing was my fault all along. Mlew in post #39 had it right- I had cut my shielding too short on the switch side, and just a few strands were enough to ground out both (yes, I screwed up both of 'em) P-leads.

30 minutes later, I had the engine running with correct ignition. Mag check and grounding check went as expected.

My wiring is: ACS switch diagram wiring, Dynon pickoffs and resistors for the RPM, ONE end ground shielded at the mag.

Reading/using the ohmmeter better was a valuable lesson here.

I sincerely appreciate all the help and time from everyone who has chimed in on this thread- and I apologize to those who are rolling their eyes at me from behind their keyboard!

Time for some liquid reward, and time to email the DAR!!!

Dave B


All times are GMT -6. The time now is 09:09 AM.