Unable to turn off primary magnetrons

Firewall Forward Aerovee
1

Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 1:18 pm

by 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?

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 1:49 pm

by 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.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 1:54 pm

by 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.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 2:14 pm

by 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.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 2:32 pm

by 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.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 3:48 pm

by 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.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 4:10 pm

by RodgerC

ACV-SB-051415

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 4:39 pm

by Rynoth

RodgerC wrote: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

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 5:30 pm

by 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?

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 6:05 pm

by 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

2

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 6:12 pm

by Rynoth

Jake, good advice for general grounding, but aren’t the magnetrons independent of the battery altogether? I’d think that connecting the p-lead to the body of the mag would be the most foolproof way to ensure the mag can actually be shut down.

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 6:25 pm

by SonexN76ET

Ryan,

I think the issue is the need for the common ground between the switch and the engine block and then the P lead when the ignition switch is switched to closed (off).

The Aerovee manual says not to put a wire from the P lead to the magnatron body but it does not specify a reason. I assume that is for normal wiring. I do not know if it would cause damage or not.

Please let us know what you find out in your trouble shooting.

Thanks!

Jake

Re: Unable to turn off primary magnetrons

Posted: Thu Nov 05, 2015 6:35 pm

by Rynoth

SonexN76ET wrote:
The Aerovee manual says not to put a wire from the P lead to the magnatron body but it does not specify a reason. I assume that is for normal wiring. I do not know if it would cause damage or not.

Jake

Electrically I don’t see a difference between wiring p lead to mag body versus wiring p lead and mag body to common ground, so I’m thinking it’s the most foolproof way to verify I don’t have bad mags. Again, I agree with your reasoning for the final setup but at this point I just want to be sure I don’t have bad mags, then I can work backwards. Unfortuantely it might be a week or more before I’m back at the hangar, just trying to brainstorm ideas. Essentially, I just want to be sure my mags can actually be killed!

Re: Unable to turn off primary magnetrons

Posted: Fri Nov 06, 2015 10:29 am

by Klimek

During the initial few hours of flight testing I noticed upon shut down my engine seemed to continue to run after electronic ignition was off and then the
magnetron turned off. At first I was unsure of what was going on. It got worse and after 10 ± hours I saw the tiny tach (back up) still displaying RPM and the engine continued to
run albeit rough. Contacted Sonex and they sent two new coil assemblies. (magnetrons) Problem solved. there was a few in a bad batch that got shipped out.
I have ground wires going everywhere to avoid the problem of non-grounding magnetrons and stop any radio noise, charging issues, etc.
By adding ground wires to the mounting screws on the mags was one way to be sure they were grounded.
I disconnected the P-leads, ran separate P-lead wires, started the engine and grounded the add on p-lead wiring and the engine continued to run…Proof positive
(to me) they were internally bad. I am by no means an engineer, however if a magnetron is grounded, it should die…
I know some engineer (s) out there is going to find fault with my reasoning and give my heck. “You know, Frank, at -114c with the quark inversion, the nutrinos can
bridge the riparian zone gap and cause a washout of the resistance core and collapse any grounding bridge”, yada, yada, yada…
Go ahead. I can take it. :wink:
Frank
ONEX090
N197u0T
37.00 hrs

Re: Unable to turn off primary magnetrons

Posted: Mon Nov 09, 2015 7:06 pm

by Rynoth

Following back up on this, today I ran a chain of ground wires along both magnetron mounting bolts to the engine block, and from there to battery negative. I still could not turn off magnetos using my switch. I then ran an additional wire from the p-leads to engine ground, and the engine still purred like a kitten. Apparently the mags are no good.

Re: Unable to turn off primary magnetrons

Posted: Mon Nov 09, 2015 7:11 pm

by kmacht

Maybe a silly question but are you sure it’s the mags staying on and not the secondary? Any chance the secondary is staying active and that is why the engine won’t shut off no matter what you do with the primary?

Keith
#554

Re: Unable to turn off primary magnetrons

Posted: Mon Nov 09, 2015 9:56 pm

by Rynoth

Keith, I mentioned earlier in this thread that I’ve eliminated the secondary as a possibility. Today I actually removed the spark plug leads from the top mag to get a sense of how the engine runs on 2 cylinders (in case I was able to actually kill 1 mag I’d know what it would sound like). My secondary ignition is 100% eliminated from this equation, and the secondary timing is still too far off to run on it alone (if I disconnect both mags)

Btw, the engine does run on 1 mag, just not a lot of hp.

Re: Unable to turn off primary magnetrons

Posted: Mon Nov 09, 2015 11:11 pm

by jjbardell

Didn’t read the entire thread but based on the topic you want to call Kerry. He told me today that some of the mags had a fault and don’t turn off.

Re: Unable to turn off primary magnetrons

Posted: Tue Nov 10, 2015 12:52 am

by mike.smith

My mags are wired: ground -to- switch -to- mags -to- ground. Nothing else.

Re: Unable to turn off primary magnetrons

Posted: Tue Nov 10, 2015 2:56 pm

by Fastcapy

-Removed-

Re: Unable to turn off primary magnetrons

Posted: Wed Nov 11, 2015 10:02 am

by Rynoth

Aeroconversions email response:

“We will send you new magnatrons. We did have a batch of magnatrons that proved defective in this manner but there is no field test for them beyond making sure the wiring is correct and then running the engine and seeing if the magnatrons can be shut off with the switch.”

Re: Unable to turn off primary magnetrons

Posted: Wed Nov 18, 2015 6:56 pm

by Rynoth

Installed my new magnetrons today. First I installed the top mag only and started the engine. When I flipped my mag switch, the engine clearly dropped to only 2 cylinders. I then replaced the bottom mag and repeated the test and the engine immediately quit. Everything now functions normally, it’s clear that my original 2 mags were both bad.

Re: Unable to turn off primary magnetrons

Posted: Mon Jun 20, 2016 9:29 pm

by ScottM-Sonex1629

Ryan:

Just ran across this older post from last fall. I had the same problems, talked with Joe at Sonex and he had me confirm the same sequence of wiring troubleshooting. My results were identical and they shipped me new Magnetrons. Completed the change out last weekend and it also fixed the problem. So there was a bad batch of magnetrons shipped at some point I pin 2014 for those still building who haven’t run your engine yet keep this in mind.

AEROVEE s/n 0766 for mine, shipped in May 2014.

Re: Unable to turn off primary magnetrons

Posted: Mon Jul 27, 2020 5:58 pm

by flyingbear

I bought a ONEX project initially sold in 2013 and my magnetrons would not shut off while I was preparing it for inspection. After lots of troubleshooting I contacted Sonex and they agreed to send me new ones at half price. They had initially years ago replaced them for free but would not for me because I had bought the project from someone else. So, I paid about $90 for two with their half price deal and found that was still about double what I could have gotten them on line for. I know they have to make money but I just do not think that is good customer service.

Re: Unable to turn off primary magnetrons

Posted: Mon Aug 24, 2020 9:26 pm

by WannaFly

Mine did the same thing—i see you contacted support. They had a batch of bad mags that would not shut off.