In search of M20 F wiring diagrams stall switch p/n

[Jpravi8tor]

I am in need of wiring diagrams for my 75M20 F I need to find the part number for the micro switch in the stall vane

does anyone have?

[Jpravi8tor]

Silly me I had the parts list the whole time! The electrical parts are listed in the back of Man 106 service manual

[KSMooniac]

You'll discover the stall vane is a purchased assembly made by safe flight, and crazy expensive to replace. It is also very difficult to remove, and properly reinstall because they are adjusted at the factory for each plane. (I'm pretty sure of that last part)

If you're having trouble, the first step should be to liberally spray electrical contact cleaner into the switch from inside and out, and exercise it. Once you get inside the wing bay to do that, you'll see why you don't want to remove it! The screws are probably corroded in place, and/or covered with lots of paint too, just to make it more fun.

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[Jpravi8tor]

You are correct this doesn’t look fun or easy! I can’t quite tell but are these actual nuts on the backside of the screws?

I tried getting my arm in the inspection panel hole but no dice!

Me thinks I need one of those skinny left handed long armed mechanics that are rare to find!

[KSMooniac]

Yes, those are nuts. You can see the slots to adjust it for the specific airplane. You can't use nutplates or rivnuts unless there were slots in the wing, and that's a bad idea.

Start with contact cleaner first.

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[M20F]

Start with the simple things first.  There is a bus bar at least up on my F that stall horn, gear horn, etc.  feed into.  Old planes = corrosion.  It’s amazing sometimes what a wire brush and dylectic grease can do. 

[Guest]

3 hours ago, Jpravi8tor said:

You are correct this doesn’t look fun or easy! I can’t quite tell but are these actual nuts on the backside of the screws?

I tried getting my arm in the inspection panel hole but no dice!

Me thinks I need one of those skinny left handed long armed mechanics that are rare to find!

For your model year, Mooney made one giant wire schematic that covered the entire plane, so you can’t just get the stall warning circuit.  But it’s the simplest of circuits, the lift detector is the end of the circuit and provides the ground for the horn/buzzer. You should be able to work it out with a volt meter and a ground jumper.

Clarence

[Guest]

You can also get rid of the Safe Flight switch in favour of a Mooney Kit.

[EricJ]

3 hours ago, Jpravi8tor said:

You are correct this doesn’t look fun or easy! I can’t quite tell but are these actual nuts on the backside of the screws?

I tried getting my arm in the inspection panel hole but no dice!

Me thinks I need one of those skinny left handed long armed mechanics that are rare to find!

There's an existing thread with a lot of good info and a few good examples of rehabbing those switches, which are essentially unobtanium or rediculously expensive.   I'd +1 on trying to clean the wire contacts (if they look corroded) and spraying it with some contact cleaner first, as it's a little sketchy to take apart, but not terrible.

It looks like one of your fasteners is missing if you didn't already take it out.   There should be two, they're both self-locking nuts on screws, and difficult to get to.
 

 

[Jpravi8tor]

Thanks guys all good info

[Marauder]

Circling back to this, access is blind and very limited, and you need to be able to get your elbow through the small oval inspection panel that provides what little access there is.  Mine barely fit.  The nuts are 5/16”.  I used an ignition wrench for the bottom nuts and a socket with an extension but no wrench for the top.  A helper to turn the screw driver would have been very helpful, especially on the top, but I didn’t have one and it is doable without one. 

Times like this is when it is great to be friends with the Lilliputians.


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[Ragsf15e]

On 7/10/2022 at 3:07 PM, M20Doc said:

You can also get rid of the Safe Flight switch in favour of a Mooney Kit.

If it’s obtainable, any idea how much the Mooney kit costs?

[Guest]

1 hour ago, Ragsf15e said:

If it’s obtainable, any idea how much the Mooney kit costs?

No stock at the moment, but last MSC wholesale(same for everyone) was $570.00US.

Clarence