New single Pmag on an O-320

[birddog486]

Originally Posted by Mark33

I have this exact setup with my dual p-mags on my -4. I have two DP three position switches. Off/ON/(ON). They also have a lockout between the on and off position so that I can?t inadvertently turn them off and it forces me to pull the levers up to put them in the off position.

Mark, do you have a diagram how these are wired. I'd like to copy this when I wire up my pmag.

[Bavafa]

Originally Posted by Bcone1381

I was kind of thinking about a single three position mag switch .....Off-On-(On) where the last position is spring loaded and removes ship power from the P-mag. Switches are lighter and cheaper than a CB, and the CB life cycle of CB that gets cycled often is a consideration to me.

Beside the things Bill has mentioned, consider that the three position switch will either require both hands to be involved (one to hold the switch and one to work the p-lead switch) or turn the p-lead to your other mag to off and work the power on your PMAG. Not that this is not doable but I would want my test to be as simple and straight forward as possible.
Here is what I have done, which does not mean is the correct/best way to do it but it has been working well for me.
I have a two position switch (ON-ON) which one leg is connected to the PMAG and the other leg feeds a LED warning light above the switch. The function of the LED is 1- to visually warn me if I have left the switch to OFF for the PMAG, 2- if for any reason my fuse to the PMAG is blown and there is no power on the wire.

[Mark33]

Originally Posted by birddog486

Mark, do you have a diagram how these are wired. I'd like to copy this when I wire up my pmag.

I don?t have an actual diagram but basically all I?m doing is using the middle (#2) position as ?on?. Then I?m grounding ?killing? the ship/battery power in the (#1) (off position). Then grounding ?killing? the self generating power lead in position (#3)...the momentary position. So here?s the sequence:

1. Flip both switches from the (#1/off) position to the (#2/on) position.

2. Start the engine.

3. At engine idle move one of the switches back down to the #1/off position while leaving the other switch in the #2/on position. This is checking ship/battery for the opposite mag. If the engine keeps running you?ve now confirmed that the engine will run on one mag/ship power on that one particular mag. Repeat this step with the other switch in the off position. You?re now confirmed that the engine will run on each individual mag/ship/battery power.

4. Now, with both switches in the middle (on/run) position, run your RPM?s up to about 1500. Move one of the switches to the (#1/off) position and move the other switch into the (#3/off/momentary) position. You?ve now killed the battery power lead on one mag and kill the p/lead (self generating power) on the other mag. The engine is now running on one mag/self generating power. Now, move both switches back to the middle position and repeat with the opposite switches. You?ve now confirmed that the engine will run one only one mag while generating its owner power...(no ship/battery power).

5. Finally, confirm that both switches are back in the middle/on positions and you?re now ready for flight. It takes less than 10 seconds to perform a complete test.

Like I?d mentioned in my previous post, my switches have a lockout between the #1/off and #2/on positions. This prevents me from inadvertently moving either switch back into the #1/off position. If one or both switches were to accidentally be moved into the #1/off position, it would continue to run just fine while your flying, but when you slow down for landing, and if both switches were in the #1/off position, the engine would die because you?re not generating self power and you?ve killed your battery power. If I were to accidentally bump a switch up into the #3/momentary position while maybe flying through turbulence, it?s not a big deal because it?ll immediately return to the #2/on position on its own. In your case I think you?d said that you?re planning to use only one p/mag, but you?d basically go through the the same sequence to check the one p-mag while killing power to your regular mag.

I hope this helps you out a little bit.

[sahrens]

I wired my P-Mag as their manual suggests with a separate switch. Here is an image of that setup.



It is easy to use and test the P-Mag.

[Scott Hersha]

The 3 position OFF/ON/(ON) toggle switch is available from Stein. Look for ?Pmag switch?. My two Pmag 3 position toggle switches are guarded with those loop guards, which make them look different than the other similar looking toggle switches on my two row switch panel, so the fact they are standing up in the on position verses forward like the rest of the switches, isn?t unusual looking.

[cojaken]

Thought ... initial adjusting via EICAD should not be a repetitive thing. Rather than installing a Dsub9 in the cockpit, I?m thinking of making up a harness to be connected directly to the Pmag temporarily when needed.

Comments?

[sahrens]

I made that harness. Although I could have done two harnesses; one for the P-Mag to D-sub and one a D-sub to the laptop,as I did not intend to change the advance once it was set that seemed a lot of work for a once or twice use.

So I made a long harness to reach the laptop. It works fine.

If I had plans to install EI Commander product I would have run the wires to the panel.

[cojaken]

I?ve got to the point where I?m ready to time the Pmag. If I understand correctly, it doesn?t matter whether cylinder number one is on the compression or exhaust stroke since the plug fires on both. The timing mark just needs to be on TDC.

Am I correct?

[Wunderon]

Here?s a sample diagram, using a 2-50

http://www.vansairforce.com/communit...5&postcount=16

[Snowflake]

Why not wire a three position switch as OFF-ON-ON, with the TEST mode in the middle? That way you move through TEST to ON when starting and running, but can drop to TEST briefly to TEST. If you forget to move back to ON, a glance will show that switch isn't UP along with the others that are UP when ON.