Unable to turn off primary magnetrons

[Rynoth]

I've wired the magnetrons per the Aerovee manual but cannot get them to turn off. I have a proper dpst switch upside down in the panel to ground the p leads seperate when the switch is down.

In testing continuity, I've found that the p leads and the body of the magnetrons have continuity, and there is continuity between the p leads and airframe ground even when I disconnect the p lead wire. The body of the magnetrons are also grounded. Basically, everything is grounded, p leads and all, at all times, and the magnetrons are always live.

What am I missing, or do I have 2 defective magnetrons?

[gammaxy]

If you connect an ohmmeter between ground and the p-lead, the ohmmeter is completing the circuit. You might notice an ohm or so of resistance due to the resistance of the coil. The measurements you describe are what I would expect. The p-lead is just one end of a coil that is connect to ground on the other end. At DC it's all shorted together.

Are you sure you don't have the opposite problem? Turning primary on and off doesn't seem to do anything because the secondary is staying on? In your other post you mentioned the engine being unable to run without primary. How are you turning them off if the switch doesn't work? Unplugging the spark plug wires?

First observations: secondary ignition timing is way off, engine wouldn't run without primary. Primary mags aren't grounding correctly for some reason, I cannot turn off the magnetrons.

[Rynoth]

Correct, I verified that the secondary was not working (bad timing, only got a few pops from flooded cylinders)by disconnecting the primary leads from the plugs. I then ran on primary only with a properly wired and verified p lead switch and could not turn them off.

[Bryan Cotton]

You have to ground the P leads to turn off the magnetrons. What is your ground path between the magnetrons and the switch? Break that ground anywhere and they stay hot. That would be the obvious thing to check.

Edit: assuming you have grounded the magnetron body to the engine per the manual, the engine needs to be grounded to the airframe if that is where you are getting ground for your switch.

[gammaxy]

Maybe try removing a ground wire from the switch and connecting the ohmmeter between it and the switch. Then you'll know if flipping the switch has any affect.

[Rynoth]

Tests:

Primary ignition switch off, both p lead wires ground to airframe and to each other (through common ground point.

Ignition switch on: p lead wires do not ground to airframe and no continuity between them.

Bodies of magnetrons have continuity to both engine and airframe.

[RodgerC]

ACV-SB-051415

[Rynoth]

ACV-SB-051415

Interesting. My Aerovee is #812 (sb went through 810) and shipped in Nov 2014. I'll contact Aeroconversions tech.

http://www.aeroconversions.com/support/aerovee_sb.html

[Rynoth]

In the interest of troubleshooting the magnetron, if I run a wire directly from the p-lead tab to the body of the magnetron, should that kill the mag?

[SonexN76ET]

Ryan,

If you ran a wire directly from the P lead tab to the body of the magnetron that would likely ground the P lead IF the magnatron body is grounded. That is actually a big IF. The question of whether the magnatron is grounded or not depends on the continuity of the ground from the battery. There is a better way to check this.

Please note that the AeroVee manual states not to wire the P lead tab to the body of the magnetron.

For the sake of testing, string a wire directly from the negative terminal of the battery to the body of the magnatron. That will ensure that you have a solid ground. Now test the magnatron and your normal wiring of the P lead to the ignition switch.

The dissimilar metals (magnesium, aluminum, and steel) do not do a good job of promoting a continuous ground. I created a common ground on my engine block from the battery and ran multiple ground wires to the items requiring a solid ground (MGL Velocity engine management system, magnatrons, oil pressure sender, ignition, etc.) from that common ground and have no further grounding issues.

Good luck!

Jake