I have the dewalt dwo56 impact driver and ive had it for a yr and i have no warranty on it ..i have a problem with the drill when i press the button for it to work it doesnt you have to shake it or tap it on the groundthe its really low torque not powerful half the times it doesnt work at all..could it be a switch or the brushes are shot

Yes they do, but did you keep a copy of them?

Where is the DEWALT® serial number on my cordless tool?

bdk.force.com > FAQ > PKB_Article
Mar 8, 2017 - Traditionally, serial numbers for DEWALT cordless tools have been located on the ... Just below the QR code is the serial number for this drill.

faulty trigger switch suggest to clean the inner part of switch or insulate seized wire or renew faulty trigger stitch

Mick, this could be a sign of a worn out/faulty motor, mine did this, ripped it apart and it was the motor. Yours may still be under 3 year warranty if you can find your receipt.
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DeWALT DCF885C2 Type 1 20V Impact Driver Parts
http://www.mmtoolparts.com/store/dewalt-impact-driver-parts
http://www.dewalt.com/en-us/legal/warranty/general-warranty-information
DEWALT ServiceNet

Did the light on the charger indicate that it was charging? (Most also have a "replace battery" or similar light.)

If so, and the drill keeps beeping...since it's new don't bother monkeying with it. Just take it back to the store and have them replace it. Dealing with a warranty repair will leave you without a tool for some length of time.

I have the same exact problem with my ryobi impact driver. I checked on my warranty first and i still have it, next I have to find the time to get it to a place so they can repair it under warranty. I'm pretty sure it's one of the boards that's connected to the trigger that's broke. Check your warranty if not check ebay for the piece. hope it helps!

if i'm confused i'm sorry, but don't confuse and impact driver with a hammer drill

2 different tools altogether

A certain amount of sparking is NORMAL, especially while the brushes wear in and seat. Keep your warranty handy though !

if the battery are less than a yr old should be a warranty
if drill DC920 or DC925 they are on recall for switch. may be co'z the battery to die. have them check at ur nearest service center.

you can't get the outer ring gear by itself. you gonna have to get the whole impact assy.

all drill has brushes. this particular drill you need a motor assy
or switch. vibration & heat are common problem cu'z the drill not to properly