Gear warning microswitch on M20J throttle

[Martin S.]

Morning everybody,

I’m trying to understand how the gear-warning microswitch on the throttle cable works on a J. I expected a groove in the cable that would deflect the switch arm and open/close a circuit, but that doesn’t seem to be the case since the cable appears smooth. There’s a small wheel/roll on the switch arm — but how does it measure the cable’s deflection?

Thanks,

 

Martin

[ArtVandelay]

There is a notch, pull the throttle out, if it’s quiet you will hear a click.

[PT20J]

The shaft from the throttle knob has a swaged connection to the flexible cable. The swage makes indentations every 90 degrees around the cable. Some people use one of the indentations as a notch for the switch. I’ve found it more reliable to have the switch roller hit the end of the shaft where it meets the cable as there is a larger jog here.

[Yetti]

I think your microswitch wheel holder is bent.   It should be at a parallel to the inner cable..   That is letting switch stay on and probably sounding the sonalert when it is not supposed to sound. 

[Martin S.]

Thanks everybody!


Sent from my iPhone using Tapatalk

[DC_Brasil]

Hello everyone. 

Reviving this topic because I was trying to find information in my Service Manual regarding adjustment of this warning and couldn't find it. I can find the airspeed microswitch calibration procedure but not the throttle-related warning.

Interestingly, my service manual doesn't have the chapter 76, titled engine controls. It has a "Currently Not Used" text. I imagine this section would contain this info.

According to the POH, the gear warning horn should sound with gear up and throttle less than about 12" MAP. Mine sounds at around 17". Consequently,  it is very annoying in descents.

Can anyone shine a light? Or perhaps some additional pictures? I was thinking if I could adjust it during next oil change. 

[Yetti]

5 hours ago, DC_Brasil said:

Hello everyone. 

Reviving this topic because I was trying to find information in my Service Manual regarding adjustment of this warning and couldn't find it. I can find the airspeed microswitch calibration procedure but not the throttle-related warning.

Interestingly, my service manual doesn't have the chapter 76, titled engine controls. It has a "Currently Not Used" text. I imagine this section would contain this info.

According to the POH, the gear warning horn should sound with gear up and throttle less than about 12" MAP. Mine sounds at around 17". Consequently,  it is very annoying in descents.

Can anyone shine a light? Or perhaps some additional pictures? I was thinking if I could adjust it during next oil change. 

The best way to do this would be note while flying where the throttle knob is at 12".  Possibly measure it several times with a ruler so you know.    Then when back on the ground set the throttle to the same position.   Then adjust the microswitch by loosening the two pretty small nuts and moving it back and forth.  

[DC_Brasil]

It is accessible from under the panel or behind the center pedestal? Anyone has pictures?

I can't seem to find this switch or procedure in the Service Manual.

[Fly Boomer]

On 11/5/2025 at 4:02 AM, DC_Brasil said:

Reviving this topic because I was trying to find information in my Service Manual regarding adjustment of this warning and couldn't find it.

Your post made me curious, so I looked in a SMM for both the J and the K.  I couldn't find a procedure in either document.  It is possible there is something in the SMM for later models.

[ArtVandelay]

It is accessible from under the panel or behind the center pedestal? Anyone has pictures?
I can't seem to find this switch or procedure in the Service Manual.

Yes, you can access it from under the panel.

https://mooneyspace.com/topic/21059-throttle-switch-for-gear-position/

[skykrawler]

On 11/5/2025 at 5:02 AM, DC_Brasil said:

Hello everyone. 

Reviving this topic because I was trying to find information in my Service Manual regarding adjustment of this warning and couldn't find it. I can find the airspeed microswitch calibration procedure but not the throttle-related warning.

Interestingly, my service manual doesn't have the chapter 76, titled engine controls. It has a "Currently Not Used" text. I imagine this section would contain this info.

According to the POH, the gear warning horn should sound with gear up and throttle less than about 12" MAP. Mine sounds at around 17". Consequently,  it is very annoying in descents.

Can anyone shine a light? Or perhaps some additional pictures? I was thinking if I could adjust it during next oil change. 

 

One case I have personally seen is after an engine installation the angle of the throttle lever on the fuel injector was not set correctly.  This resulted in the throttle cable position being further out for a given manifold pressure.   This was on a K model, but I suppose it can happen on a Lycoming installation in a J.

 

[Yetti]

5 hours ago, DC_Brasil said:

It is accessible from under the panel or behind the center pedestal? Anyone has pictures?

I can't seem to find this switch or procedure in the Service Manual.

on the backside of the panel mounted to the throttle cable.