My sds drill (Bosch GBH 2-24 DFR) has developed a fault when sometimes you pull the trigger and get nothing, tip it vertical (or maybe give it a knock) and it's ok.
I've had it apart and checked for low-ohm across every single connection - coils, brushes, reversing switch and main switch - all exaclty what you'd expect.
The fault seems orientation dependent - particularly pronounced when it's horizontal (tip it off horizontal and it runs fine, back to horizontal and it doesn't, tip it downwards and it's ok again, back to horiz - arrrgh! - etc).
The only thing I can't check is the speed-sensitive part of the switch (there's a direct contact as well- for the supressor cap - which I can check, and is ok).
So how do these speed senstive switches work? Is there a variable resistance in there?
The power switch is =A326, so unless it's a fairly certain suspect, I'd be reluctant to buy one.
Parts diagram here: