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alpinelakespilot2000

Well Known Member
Edit: I originally had some letters mixed up. Fixed them in the narrative below...

Need some help. Went to wire my mags (at the mags) using Bob Nuckoll's Z-26 diagram. They are already wired at the ignition switch. I used a solder sleeve from Stein to ground the shield (C) at the mag. Tested for continuity between C and D, expecting to get none, I found that indeed I do have continuity there. (The mag switch is in the OFF position.) Thinking maybe the solder got through the insulation onto the p-lead wire, I cut the solder sleeve off but found the continuity still exists. Not only that, but I have continuity at A and D as well. I do not have continuity at B and C, or A and B. Is this how it should be or have I done something wrong? I THINK I might be OK given the chart shown below the wiring diagram, but am not at all sure.

Thanks for humoring my lack of knowledge about mags!

 
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I bet if you put your ohmeter from the p lead post to ground with NO p lead attached you'll read the same thing. you're reading "continuity" through yhe magneto capacitor (same reason you can't check timing with an ohmeter). Check your p leads while detached from the magneto, I bet you're okay. Fun huh?
 
I just re-read this, duh. If your mag switch is OFF, then both p leads will be grounded throught the keyswitch. Open circuit with switch on. You will still read a ground through the magneto capacitor though.
 
The p-leads and shields are not connected to the mags, they're just loose and that's how I tested them.

I am surprised that the 2 shields (B and C) don't show continuity with each other though. It seems from the diagram that they should.
 
If your key sw is off...you should have 0 ohms res from any p lead to any shield meas at engine with or without wires connected to mag.

If I meas res at mag from plead term to ground I get 2.75 on left and 3.25 ohms on right.

Both shields should be connected to gnd term at switch. Then both shields get grounded through mag grounds only.
 
OK, let me ask this, or ask it this way:

All wires connected to their respective terminals at the switch, but nothing connected at the mags. Even though B and C are connected to the same switch terminal (GRD), I get my continuity tone at B and C (the mag end of both shields) only when the ignition switch is OUT of the panel. When the switch is in the panel, I get no continuity tone between B and C. At first I thought I just had a loose terminal or bad crimp, but the discrepency only seems related to whether the switch is in the panel or out. It's almost like the switch casing is grounding to the panel causing the discrepency. Still, I'm not sure why in or out of the panel would matter since both shields connect at that GRD terminal. Does any of this make sense? I'm wondering if I've got a problem or if everything is as it should be.

 
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Take switch out, disconnect all wires. Now, do as I did before I installed switch (or anything in my plane for that matter)...

Do continuity tests on terminals per diagram. If they don't jive you have a bad switch. If they jive then you need to redo wiring.

The grd term on sw is not supposed to be grounded to sw case otherwise it would cause ground loops. We only want shields grounded at magneto grd terminal.
 
Thanks Wayne. I think I got it. I traced the problem down to an intermitant solder sleeve on the right mag p-lead on the switch end. As I pushed the switch in and out of the panel it was just enough to flex that solder sleeve and break the connection. I reheated the solder sleeve and that seems to have flowed the solder better onto the shield.

The irony is that I had that the p-leads put together originally using a terminal on the twisted shield, well supported by heatshrink as per the EAA website video. A lot of people here on VAF mocked that method and said solder sleeves were better so I went that route! :rolleyes:

Now, A, B, C, or D all provide continuity when connected with any of the others (A, B, C, or D) when the mag switch is in the off position. I believe that is the way it is supposed to work. If anyone thinks otherwise, please let me know.

 
I used crimp on ring conn. I have used solder sleeves too in other places. Both are satisfactory if done properly. I really don't think there is enough solder in those sleeves and they are higher priced. Some don't like ign sw like we have either. Build for you and nobody else. Try different methods and materials and see what works for you.

If you do every mod, prime every piece, buy the latest gadget, and spend to much time on VAF we will never finish. Good luck. I hope to be flying soon.
 
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