Drip type coffee makers should be made a party of your regular kitchen cleaning routine (at least once a month). Dried coffee oils can ruin the taste of even the best blend. In addition, if you have what's considered "hard water", minerals can build up inside your coffee maker.
An alternative to commercial coffee cleaners is to run a solution of half white vinegar and half water through the coffee maker to dissolve scale. The heated solution may have to be run through the unit one or more times if buildup is heavy. Thoroughly rinse all parts of the unit.
Run plain cold water through a cycle to remove all traces. If you still have your owner's manual, check it as well for instructions specific to your model. The glass pot, filter container and other removeable components can be cleaned when you're washing the dishes.