Dewalt cordless drill dc988- drill motor works intermitantly when trigger is pulled. Works a little better as it warms up. Im thinking vsr switch, brushes, or motor/armature. please help...

Your switch is having a problem it can be caused by excessive load on the motor.
The motor must be sounds not shrill and must have power , the most people think on the batteries but in more case by switch problems its the motor there is a field effect transistor inside the switch behind the cooling brass plate thats shorted and that is for the variable rpm .
Replace switch and if the motor sounds good then the problem should solved. if also the motor is bad go for a new replacement body ask your dealer.

web search-dewalt dc988 schematics-click on 2nd site,{parts list and diagrams

Just buy a new Makita 18volt.

http://www.ereplacementparts.com/

check that it isnt lock halfway between forward and reverse,iv seen it happen.

you can go to Dewaltservicenet.com and in the middle of the page towards the bottom you will find a box for manual. Type in your model number and you can download a schematic for the tool.

Ok, first check to see if the trigger lockout has been engaged, it's a small level at the top of the trigger ( I know this sounds silly, but it happens sometimes). Flip it side to side to see if you can hear the selector moving the switch inside the drill. If the selector moves freely without engaging the switch, you'll have to disassembly the drill housing to put the selector back into the lever so it will work.

Just take out all the screws in the housing and carefully remove the one side and look at the switch lever and make sure it is inside the slide selector lever.

If that isn't the issue, I'm afraid that the electric trigger/switch has failed and this isn't a part that can be disassembled and repaired by a DIY'er. I've attempted it when mine failed and found out it's a sealed unit and wrapped in a copper heat shield that dissapates heat when the variable speed is utilized and you end up destroying the switch housing in the process.

However, any DeWalt authorized repair center can do the repair for around $20 +/-, and if your drill is under the 3 year warranty period, it should be a free, warranty repair. Just contact DeWalt's customer service or your local Authorized Service Center (listed in phone book usually), or check the link for finding one near you.

www.dewalt.com or call 1-800-4-DEWALT (1-800-433-9258

Click on the "Services/Support" tab to get info. You can also buy the replacement parts if your drill is out of warranty (call them to verify before takin it apart!) and do the repair yourself.

Hope you find this Very Helpful and best regards!

Hello,
Here is a link for a parts diagram for your model. It has the proper part number that you will need.
Hope this helps.

http://www.toolpartsdirect.com/cgi-bin/schematic.cgi/dewalt/DC988KA_TYPE_1

I have been rebuilding drills for 10 yrs and have installs hundreds of switches. This is not an issue in a switch like this. If it was, the energy from the motor working should damage the switch more than the static from your body. I would not be concern with it.

It depends on what you mean by intermittent. If the drill takes a few tries to turn on, but works fine once it does, it usually means there's a problem with the switch. If the power is weak and tends to cut out, it generally means there's a problem with the motor - usually brushes. This article might clear things up a bit:

Whodunnt? The brushes or the switch?

You can get whichever part you need replaced on that same site.