Problem with cordless drill-driver

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Interior designer / Decorator
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Hi, I'd be really grateful for any help or advice!

Once a battery is attached to my Bosch cordless drill/driver, the drill will only work the first time the switch is pressed. As soon as the pressure is released, it won't work again until the battery is removed, then replaced. Then, once again, it'll only work the first time the switch is pressed. And so on. And on...

Other functions are ok, except that the light comes on and remains on for no reason when the drill is not in use, obviously draining the battery.

Situation is the same with different batteries.

Please can anyone help diagnose this fault for me, and advise me on whether there's an easy fix? Or is it time to dump the drill and buy another, seeing as it's out of warranty?

Grateful thanks in advance for any suggestions.

Best wishes,

Sandpeeps.
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Joinery installation in the broadest sense
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Hello sandpipa.
This sounds very frustrating.
The way you describe the problem, I'm not sure there is an easy fix. First thing to check, and I know you've tried a few batteries, but check the batteries are seating properly. For example, if you hold the drill chuck up, are you still having the problem?
If the problems not there, it could be your drill is activating the ECP (electronic cell protection) when it doesn't need to be. As the drills out of warranty, open it up and have a look see. Take an alchohol wipe and give things a good clean around the elctronics module. You might get lucky and that's all it needs.
It could be one of the two sensor wires from the battery terminal to the board. There's 4 wires altogether - the red and black are power - it's the other two I'm refering to. If one of these is starting to give it might cause the drill to misbehave. Might mean removing the heat shrink to check the connection. Above where it's soldered is a weak point.
It could well be that a MOSFET has gone or going on the board. For most folk this is terminal and means either replacing the electronics module or the drill.
There's a number of things it could be to be honest.
Powertoolspares.com is pretty comprhensive for spare parts. You could always contact a service centre and see what they say. I'm not sure but I think you'l get, or can request, a quote before they fix it.
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Roofer / Carpenter
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Hi all,

So I'm responding to this question several months later because I had the same problem Sandpeep described. The drill is a few years old, and only sees occasional use around the house. I'd hope to get a few more years out of it.

I threw my battery on the charger (even though it showed a full charge on the first startup as Sandpeep described) and pulled the clamshell apart as Bailey suggested. There was a fair amount of dust inside, which I removed with a small brush. This was particularly true on the circuit board on the bottom. Could well have been shorting something.  Screwed the thing back tight together and hooked up the battery. Problem solved. Thanks to Bailey for the suggestion, and hope this comment helps the next person who comes along. 

-JC
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Joinery installation in the broadest sense
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Hello JC
Glad the clean out option worked for you. Surprising how often this is the case with electronics faults.
Thanks for checking in and letting folk know what worked for you. Others will find it useful I'm sure.
All the best. 
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Other building trade
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I've had complete failure of the electronics modules on several power tools now from bosch.  Out of warranty.  It is annoying as the tools are good.  The modules are not cheap and seem to be more of an issue with bosch tools.  I won't be buying bosch again.  Such a shame as I've always been a big fan of their stuff. I'm pretty sure the repair would be cheap and fairly easy too.