Unknown electrical switch in M20C 1967.

[pilot-as14]

Hello,

Unknown electrical switch in my M20C 1967. Can someone please tell me where this little poisonous gnome is installed and what it's supposed to do on the plane?

Many thanks!

[hammdo]

Gear warning switch that is supposed to be on the throttle. Should kick on the sound when below a certain manifold pressure based on throttle position. I’ll see if I can find the thread…
 

-Don

[hammdo]

-Don

[chriscalandro]

Based on the way those wires are cut you can put this into one of two categories - 

option 1 - "Things I wish I hadn't removed

option 2 - "Things I wish that other person hadn't removed"

Working with what's left of that wire isn't going to be pleasant.

[AIREMATT]

30 minutes ago, chriscalandro said:

Based on the way those wires are cut you can put this into one of two categories - 

option 1 - "Things I wish I hadn't removed

option 2 - "Things I wish that other person hadn't removed"

Working with what's left of that wire isn't going to be pleasant.

Option 3 - “Do I know if it still works?”

[MikeOH]

1 minute ago, AIREMATT said:

Option 3 - “Do I know if it still works?”

Do you have an ohmmeter? That will confirm switch operation. A couple ring terminals, proper wire and crimp tool and all will be good. 

[carusoam]

Fastest way to look for the gear warning switch…

peek under the panel to find the throttle location switch…

 

Best way to know what that switch is…

look up the part number in the parts catalog…

 

that was removed for some reason…

they don’t usually fall out…

 

Best regards,

-a-

[AdamJD]

Another thread that shows this in action:

 

 

 

[Bob E]

First ever reference to a Giftzwerg in Mooneyspace! 

[jamesm]

Not the best picture ....  attached is how it is installed in my '67 M20C.

If memory serves me correctly.... The book says you should get gear warning at 10" MAP Manifold pressure.

Hope this helps,

James

 

 

 

[Hank]

1 hour ago, jamesm said:

If memory serves me correctly.... The book says you should get gear warning at 10" MAP Manifold pressure.

For my 1970 C, the gear buzzer comes on at 12".

[jamesm]

Not sure what changed, or  why it was changed, between 1970 and 1967 'C' models per my 'Mark 21 MODEL M20C 1967 Owners Manual' MOONEY AIRCRAFT, INC. it has no revision markings.  Not sure how big of a factor  2" of Manifold pressure makes nor am I sure of the tolerances.

[jamesm]

Here is a print of the electrical schematic for a 1967 M20C. I believe this is a traced copy from Mooney Parts Catalog. <for reference only>

Hope this helps,

James '67C

[carusoam]

There is a bit of a sweet range…

too high… the horn comes on while slowing the plane before the gear comes out…. This keeps the pilot busy holding the switch in the gear down lock block hole…

 

too low… the horn doesn’t come on until pulling the power out, when the runway is made….  This is a bit too late for a surprise… very easy to ignore with all the other things going on.

 

Better to come on early, than to not come on until late…

One is annoyance… the other gets ignored when the brain is already busy with the landing details…

 

Any oddities on short final…. Feel free to go around!!!

A typical surprise… you have put the gear down… and the throttle alarm goes off on short final…

This happens to mechanical gear with a worn down lock block… make sure the gear is locked… (thumbnail test, pull the handle down, see the green light…) 

 

PP thoughts only, not a CFI…

Best regards,

-a-

[bcg]

On 3/28/2023 at 5:54 PM, chriscalandro said:

Based on the way those wires are cut you can put this into one of two categories - 

option 1 - "Things I wish I hadn't removed

option 2 - "Things I wish that other person hadn't removed"

Working with what's left of that wire isn't going to be pleasant.

Looks like that wire is connected to the switch with a screw so replacing it with one of the proper length should be a non-issue.

[DXB]

It took a while to get mine adjusted right - it's damn annoying if it goes off at MPs >>12.  I could see someone tearing it out from frustration even though it is a useful safety feature when correctly adjusted.  It would be nice to upgrade the horn for it, along with the stall horn also, to less abrasive and more modern-sounding noise makers - has anyone done this?

[ArtVandelay]

I would be deeply concerned that a safety device was removed and there probably is no log entry. Make you wonder what else they did.

[chriscalandro]

6 hours ago, bcg said:

Looks like that wire is connected to the switch with a screw so replacing it with one of the proper length should be a non-issue.

That’s the gnd side. The other cut wire, the one I mentioned is not. 

[carusoam]

12 hours ago, DXB said:

It took a while to get mine adjusted right - it's damn annoying if it goes off at MPs >>12.  I could see someone tearing it out from frustration even though it is a useful safety feature when correctly adjusted.  It would be nice to upgrade the horn for it, along with the stall horn also, to less abrasive and more modern-sounding noise makers - has anyone done this?

Hey Dev!
 

Might want to check with your favorite maintainer…

Mooney parts from the 90s would possibly be an interesting improvement…

Might be a simple electronic box /tone generator using the same switches we have in all Mooneys…

A simple speaker in place of the sonalert might be the big pain… removing the ceiling to gain access to the space…

The only thing that changes… the stall warning stops working if you turn the master off prior to an off field landing….   
 

PP thoughts only, not a mechanic… or electrician…

Best regards,

-a-

[Denis Mexted]

My 2 cents. I can't imagine someone would disable the gear horn.

I can on the other hand imagine they would remove the Ram Air function. This drives the Ram Air annunciator light. 

[Denis Mexted]

Having said that, I'm not so sure a M20C '67 model has Ram Air.

What other switches would it have? 

 

[bcg]

17 hours ago, chriscalandro said:

That’s the gnd side. The other cut wire, the one I mentioned is not. 

I must me missing something because those sure look like screw terminals to me...  I see small, flathead screws in them.

[chriscalandro]

8 hours ago, bcg said:

I must me missing something because those sure look like screw terminals to me...  I see small, flathead screws in them.

The wire that goes to that screw terminal is cut. Getting to that wire, which is now shorter, is going to be an unpleasant experience. 
 

There is no ring on the cut wire to go to the screw terminal. 
 

you should go do it for him. 

[MikeOH]

6 hours ago, chriscalandro said:

The wire that goes to that screw terminal is cut. Getting to that wire, which is now shorter, is going to be an unpleasant experience. 
 

There is no ring on the cut wire to go to the screw terminal. 
 

you should go do it for him. 

OMG!

You mean someone will need to SPLICE a wire!!  Oh, the horror, the horror...

[chriscalandro]

You think splicing a wire correctly, behind the panel, with likely less than 2 inches of wire to deal with, in between the engine controls, is going to be a simple task?

 

i’d LOVE to see you do it.