E-Mag Shielding Question

[Dad's RV-10]

From Stein...

PMag Power Test

The wiring diagram in the link quoted above was posted in another thread. It shows shielded wire for the P-Mag P-Lead.

The P-Mag installation manual says, "E-MAG kill (p-lead) wire does not make radio noise and does not require shielding. If replacing a magneto, your existing shielded p-lead wire can be re-used. If doing so, the outer shield needs to be trimmed clean and kept well clear of all other terminations."

I assume the Stein diagram shows shielded wire for the P-Lead only for those who are swapping from traditional mags to E-Mags and likely already have shielded wire in place?

 

[wirejock]

Correct. But I did use shielded. If you notice, the shield is grounded at the engine case and acts as the ground for the p-lead when the switch is off. That's also program position. Power and grounded p-lead puts the mag into program. If you are inclined to use EICAD.
If shielded isn't used, you need a ground to the switch.

 

[Dad's RV-10]

If shielded isn't used, you need a ground to the switch.

Thanks. The plane was built new (years ago) with dual P-Mags. It has an ACS switch, two momentary P-Mag test toggles and two respective P-Mag circuit breakers (and no shielded wire). I want to replace the ACS with a push-to-start switch and replace the two momentary toggles with ON-ON-Momentary toggles.

As best I can tell, the two wires on each existing momentary toggle simply interrupt power from their respective breaker to the respective Pin 5 on each P-Mag.

The only ground wire is on the ACS switch, which is where the existing Left and Right P-Leads (P-Mag Pin 4) are also connected.

My plan is to simply jumper the existing ACS ground wire to each of the two new ON-ON-Momentary switches.

The new push-to-start button should simply bridge the wires that are now connected to the ACS 3 Bat and ACS 4 Starter Solenoid terminals.

 

[wirejock]

Thanks. The plane was built new (years ago) with dual P-Mags. It has an ACS switch, two momentary P-Mag test toggles and two respective P-Mag circuit breakers (and no shielded wire). I want to replace the ACS with a push-to-start switch and replace the two momentary toggles with ON-ON-Momentary toggles.

As best I can tell, the two wires on each existing momentary toggle simply interrupt power from their respective breaker to the respective Pin 5 on each P-Mag.

The only ground wire is on the ACS switch, which is where the existing Left and Right P-Leads (P-Mag Pin 4) are also connected.

My plan is to simply jumper the existing ACS ground wire to each of the two new ON-ON-Momentary switches.

The new push-to-start button should simply bridge the wires that are now connected to the ACS 3 Bat and ACS 4 Starter Solenoid terminals.

That sounds correct. The momentary switches are used to test on runup to test the internal generators. I also switch each off one then the other to make sure the engine will run on one mag. After shut down, I pull the breakers as a safety.