Bendix Ignition Switch Wiring

Gents,

I've read/searched for how to wire a Bendix ignition switch. I've removed a dead LASAR system; installing two new Slick mags and new P-leads. The ignition switch is a "Off/R/L/BOTH" switch, not "start" position (separate spring-loaded toggle switch for that)

The current ignition switch wiring has the ground post grounded to the aircraft (probably required for the LASAR system). From what I've read, you do NOT want the magneto ground wires grounded to the aircraft ground, as this could introduce "noise" into the electrical system. That would happen if I don't remove the current ground wire. The ground wire of the P-leads should be grounded at the ignition switch post and at the mags, and that's it.

So if I understand correctly, I'll want to disconnect the current ground wire, and attach the two P-lead ground terminals at the ignition switch ground post. Is this correct?

Thanks!

Still looking for help here.

I believe you are correct.

Thanks, Bob.

I realize my question is probably "basic man" level, but I've never wired an ignition switch before, and there are no manufacturer instrcutions that I can find.

What prompted my question is that, when I was connecting the left and right P-Leads to the ignition switch, I noticed a wire running from the ignition switch ground post to an airframe ground buss. That might have been correct for the failed LASAR system I removed (beats me if it was or not), but didn't seem like that is correct for a magneto setup.

So, best I could tell, the shielding ground lug should be connected to that ignition switch ground post, but NO wire should be going from the ignition ground post to an airframe ground. THEN, I read where only the shielding wire lug at the magneto end should be grounded at the mag ground post, and the other shield wire lug should NOT be connected to the ignition switch ground post; that only ONE end of that shielding should be grounded, and that's the mag end.

Hopefully that spells out my confusion here.

Wiring

P lead shield should ONLY be grounded at Magneto. When the Bendix switch is in the off position You SHOULD be grounding both mags. In the left mag position you are grounding the right mag, etc.
The ground from switch to airframe is probably a good idea. Ground from switch thru switch mounting to the airframe is a bit dubious. Paint on mount etc. can compromise the ground path.

Bending wiring

If you do a Google search you will find what you're looking for
Just search "bendix ignition switch wiring diagram".
danny

Both

I have seen both of the methods indicated in this thread. You are less likely to have ignition noise in your comm radio if you use the shield as the ground path instead of airframe ground. I have also seen both ground paths used.
The pro for the use of shield ground AND airframe ground is that there is less chance of the ground path being broken, resulting in an inadvertent hot mag.

Thanks for the good input.

Right now I have the ignition switch ground post connected to airframe ground, but the P-Lead shieldings are only grounded at the magnetos. I did NOT connect the shielding lugs to the ignition switch ground post. I heat-shrink wrapped the lugs, and zip-tied them out of the way.