Bosch GBH 2-20 SE hammer drill stopped working

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Take a little screwdriver under the knop and jump him out BUT be carefull there is a little metal pin inside the knob that can be loose and easy lost .
And important Jump out the knop (BEFORE) you have removed the 4 screws of the black house.

The collar of the chuck should pull back releasing it. You will have to pull back the chuck and pull the bit at the same time.

broken tooth in gearring .

see the video and fix it. God bless you

Try here at Bosch's website;

https://www.boschtoolsservice.com/Search/IPLSearch.aspx

Check that the ramped discs and the selector lever for the hammer action are assembled correctly. The lever should push the chuck shaft clear of the hammer action discs or release the shaft so that it can move inwards to allow the ramps to ride up each other.

a bad trigger switch; bosch sells a replacement part

By rotary switch I guess you mean the selector? If so it is rather easy in a way on the schematic you have you will seel that it has a pointer that the button of the switch has to face, but the key to this is that you need a small screwdriver or other object that you need to push the red button in and turn the selector past the stop and then it will pull out . Let me know if there is something I am missing and good luck. If I have answered your question would you please rate my solution accordingly.

Go to Boschtools.com and type in your number or go to tools and rotary hammers and highlight your hammer, it will take you to another page and then you can look at a breakdown which is very specific on the direction and placement of the selector. The shift fork must be in the forward position and you can eyeball it with the post on the selector after you have it in position to lock it in. Remember you have to depress the plunger on the selector to reinstall it. Let me know if you still are having problems.