Impact not working correctly

find out what thread direction the screws are before going brutal---an impact driver may have to be use to remove screws---don't know if they used lock tight on them or not from factory---impact driver is a tool that you insert in to the screw then rap the end of the driver with a mallet/hammer---this action keeps the screw bit buried in the screw and twists at the same time after being hit----this will work only if there's no lock nuts opposite the screw (other end).----GL

These are known for the spring in the nose (#12) to fail.
Using an o-ring pick or small screwdriver remove the hog ring on the end of the bit holder (#17).
Slide the washer, spring, and sleeve off (Be careful not to lose the small lock ball)
The spring that pushes the lock ball forward (#12) is usually the culprit.
Reassemble in reverse order DeWALT DCF886D2 20V Impact Driver Parts

The switch is about the only thing that controls the speed of the tool.
If you post the model number I can get you the correct part#

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.
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."
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

I think that model is on a ring internally so there isnt a way to do like the bigger ones, you would have to take the screws out and take in half and you will the the brushes and can replace.

A good place to start with Dewalt tools is the switch. Take the front off the handle and pull the switch out far enough to test the posts on the back. Plug the cord in and check for voltage where the cord attaches to the switch. No voltage, bad cord, replace the cord. If you have voltage, the cord is good. With some help, hold the switch on and check for current on the motor side of the switch. If no voltage, replace the switch. If there is voltage there, you are going to have to check the brushes, armature and/or field for continuity or shorts.

Here is a schematic for you.

http://servicenet.dewalt.com/Products/Detail/DC825B

Hi there, the first thing you need to do is check the carbon brushes, there will be two of these one at each side of the motor, if these are ok then test if power is getting to the motor, to do this you will need to split the casing on the tool in half. You may need a torx driver to undo the screws on the casing. Once you have removed the screws, very carefully split the casing making sure you leave the gearbox assy, motor and switch in the other half. Insert battery onto the unit and get someone to hold the motor in place just incase the machine starts. get a voltmeter, follow the wires from the switch to the motor and where the wires attach to the motor put the probes of the voltmeter and pull the switch to engage it. You should be gettting a good voltage now, If you are then the switch is ok. hope this is of some help

its supposed to impact immediately that is what gives the tool its power. once you get used to it you will use it for everything its lighter and more powerfull than the drill. just dont use spade bits in it or it will shatter them. try to buy tips that are impact ready

Hold the chuck by its sleeve, put the drill in reverse (make sure it's set at high torque if you used it in a drill/driver) and go full speed. That should release the bit.