Landing Light Switch on 1979 M20J

[N201MKTurbo]

On 11/4/2024 at 5:44 PM, carusoam said:

Sensata doesn’t sell direct to customers… because they suck…  (plus they won’t sell just the printed switch caps)

I use aircraft spruce… they may have them  in stock, or can get from Sensata quite quickly…

+1 for holding onto your existing switch caps… they snap on and off an oversized metal body…

Landing lights of the original kind…(not LED)

use a lot of electricity and generate a tiny spark each time you turn them on… this tiny spark knocks a micro piece of metal off the contact surface…. After years of operation, the CB switch loses its over center nature…

the click gets softer and softer over time, as does its ability to resist tripping.

 

PP thoughts only, not a mechanic…

best regards,

-a-

You are mostly right about all this, but the contact points are separate from the disk that holds the switch in the on position.

The current sensing element is a bimetallic domed disk with a small hole in the center of the dome. The switch rocker is spring loaded to the off position. When you turn the switch on, a small lever swings over the disk pushing it down which pushes the contact points together. This lever has a small bump on it that snaps into the hole in the dome holding the switch in the on position. The current flows through the dome. If the current gets too high, it causes the dome to flatten out which allows the spring loaded lever to snap back to the off position, this removes the downward force from the contact points allowing them to spring open.

The switch wears out because of mechanical wear at the little hole in the dome and the bump on the lever. The hole wears bigger and the bump gets smaller and they don’t fit together very tightly after they are worn.

The contact points are very beefy and usually have a lot of life left when the domes wear out.

BTW, I have taken a few of these apart after they have worn out to see how they work and how they fail.

[William A]

I am referring to the mounting holes not lining up with my current mounting holes not the switch itself. Perhaps I could use the original mounting sleeve to hold the new switch in place with some modifications.