You are in the middle of replacing your old windows. In the excitement of your project, your power tool begins to run one minute, only to shut off the next! One moment it's working fine, just like it always did, and the next it is completely dead. You click the trigger a few times and it's running again. What in the world is going on?
Chances are that you are not out of luck. There are clues which can help you find the problem. While many problems may cause intermittent tool operation, two of the most common failures are the switch and the carbon brushes.
The switch usually sits behind the main trigger, controlling power flow from the wall to the tool. When a switch is worn out, it works less and less frequently. At first it works pretty much all of the time. Occasionally it may need to be clicked twice to start the tool. Over time, you may find yourself clicking the switch several times every time you start the tool. Of course, once the tool is running it works perfectly as long as you hold down the trigger. You probably just need a new switch.
Carbon brushes transfer power to the motor of your power tool. Carbon brush problems are a little different from the switch. When carbon brushes become marginal, a power tool will begin to "cut out" while it's running. Sometimes you might tap or slap the tool to get it running again. The trigger starts the tool just fine, but it doesn't run well. This sort of symptom usually points to a carbon brush problem. You will want to inspect your carbon brushes before replacing them. A worn out carbon brush will often have a small amount of carbon remaining, or it will be pitted or chipped. If your carbon brushes are bad, it sometimes means that your power tool has bigger problems (like a worn out motor). Quite often though, a fresh pair of carbon brushes can get you working again.