If you have only used it four times. I would take it to a Bosch service center. Tell them your story. and there's a good chance they will fix it under warranty. sound's like a manufacture defect.

I tried that .. and the repair person even called them to verify its was in new like condition... but they said NO!! I also sent them a couple of emails to their website explaining the situation , but they have failed to respond.

Your splines are probably wore out. Take the rubber nose cover off and the sleeve. Remove all the piece's the hold the bit in. Then lock the bit in a vise. Take a good size hammer and punch. hit the nose of the tool and drive the tool off of the bit.

Hey dagm,
usually what happens is the hammer mechanism [piston/striker chamber or hammer pipe] develops a dry pocket..it dries out or the lube just breaks down..check out the parts breakdown at ereplacementparts.com for the service pack..item # 897..it comes with all the o-rings that you will need along with the brush's.. they also carry the grease and oil that you will need..[the o-ring on the striker..item #57.. along with proper lube will take care of the problem] Hope this helps..:)
Craig

This is actually because part 1617000843 is made of plastic, and as such is pretty weak compared to the rest of the tool. This is actually by design, as the tool hits too hard this part will break first, protecting the rest of the tool. Of course it means you need to completely clean out the plastic shrapnel from the inside and replace all the seals (which are wear parts anyways) and then install the new service kit, adding the proper grease and all that. Its annoying, but on the plus side it does mean the tool won't spin and chew gears or shear off part of the armature shaft. Personally, I don't like it. I'd rather have a nicely built Metabo rotary hammer that's designed for years of punishment instead of this failsafe that breaks every few months.

Hey bigray,
usually the red light indicates its time for some maintenance on you tool..it will come on if the brush's wear down past 50 % or if the tool is heating up due to the grease breaking down..it also may mean there is a problem with the electronic auto controller itself..the light is saying there is a problem that needs to be addressed and if you keep using you tool the problem might worsen and be more expensive to repair..! ugh:) check your brush's first and go from there.. parts avail at ereplacementparts.com
brush assy 1-617-014-110
contoller 1-617-233-003 [also in handle kit form 1-617-000-161]
Hope this helps..
Craig