Urgent help needed - electrical trim switch (yoke)

[skykrawler]

This is the KAP-150 trim switch diagram.

[NicoN]

After completing the repair, I can give some more information of how this trim switch in our 1980 M20K works:

There are a lot of safety feaures, intended to giv you full control on the trim wheel ...

1.  We have a kind of electrical clutch which is activated by pushing down the plunger (?) of the switch. Without pressing the plunger, the trim motor moves ( as long as you operate the trim switch in up or down direction), but it does not turn the trim wheel. You only can hear the motor running

2. The motor itself is driven or energized via a relais. And this relais  cuts the power lines to the motor  in case you press the trim interrupt button .

3. the trim switch itself connects both power lines of the motor to GND as long as the trim switch is in neutral.

Someone really wants to have the motor disconnnected from the trim assembly!

 

But first to the switch:

This littke assemby has 3 micro switches of the same type and each as a normally-closed contact and a normally-open contact together with a thrid contact - COMMON.

The middle micro-switch is operated by pressing the plunger down - that's it. And it powers the electric clutch. As long as this clutch is powered by 12V, you cannot move the trim wheel by hand!

The left or right switch is pressed by moving the plunger back or forward. Only one of the switches is operated at a time - never both.

By making clever use of the normally open and -close functions  of the micro switches these 2 switches make an "H"-wiring. 

This is a typical trick to reverse a DC-motor. Simple, but working and in neutral both lines of the  motor are connected to ground.

I will show a picture of how the back of the trim switch assembly looks.

 

There is more:

Correctly connecting the wires to the switch still  does not help as the DC-motor lines are routed through an relais. Without energizing the relais your motor is disconnected and therefore not moving.

This makes it difficult to partially try the function of the trim switch. The whole assembly needs to be wired correctly to give simple 12V to a simpole DC-motor! If not - only silence.