Demolition Hammer: Excessive Sparks From the Motor

The armature is the power-producing part of an electric motor, located inside of a magnetic field. The armature has a commutator on its shaft that brushes ride on, supping power. To check this part for excessive sparks and clean or replace it, start by removing the handle. This repair procedure will vary on different models, but is similar.

Remove the screws securing the housing from the motor and take it out of the unit. Pull the armature out of the housing and remove it from the bearing housing. You can do this by placing it in a vice and use a spanner wrench to spin the cap back on. You also can place a punch in the side of the notch and tap it with a hammer to spin it loose. Remove the nut underneath the cap. Check the commutator for burn marks. At this time, you can clean the commutator with a file or sandpaper to get rid of the burn marks – this is usually the cause to sparks.

To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the windings. As you move it around the commutator, the reading number is not important. You are looking for a consistent reading, indicating all the windings are good. If it varies, radically reading zero, or open circuit, then the armature is bad. Another test is reading. If the ohm reads zero, or open circuit, then that indicates a bad armature. The last test is a bar to ground test, which is done by placing one end of the ohmmeter to the tip of the shaft of the armature and the other end to the commutator. If the armature is bad, install a new one.

Reinstall the fan and the brush holder back in the bearing housing, ensuring the tabs line up on the brush holder. Place the armature in the housing and reinstall the nut. Place in a vice to tighten. Spin the cap back on and tighten. Slide the armature back in the housing (the same way you removed it) then reattach the housing assembly back on the unit. Secure the screws tight. Reattach the handle.

The brushes ride of the commutator, applying electricity to the armature. If the brushes become worn, wear unevenly or one, or more, of the springs are applying incorrect pressure, then this can cause the motor to spark excessively. To check and replace these brushes, remove the end cap on the motor. Locate and remove the brush holders. Pull out the brushes and inspect. If they are worn more than an eighth of an inch from the wire, they will need to be replaced. Furthermore, if you notice there are burn marks, this will also require replacement. Install the new brushes and reinstall the brush cap. Lastly, secure the motor cover back together.

A field coil is an electromagnet used to generate a magnetic field in an electromagnetic machine. Over time, this part can build up a lot of heavy dirt as well as overheat, leading to problems like sparking. The following repair procedure will vary on different models but is similar.

To check this part for excessive sparks, and to clean or replace it, remove the screws securing the motor housing to the demolition hammer. Now, remove the armature from the motor housing. Clear off any clamps, brackets, and screws holding the field in place inside the motor housing. Disconnect all wires going to the field. Pull the field out and inspect for burn marks.

Any burn marks on the field indicates it is sparking and requires replacement. If the field looks fine, clean it thoroughly in thinner and dry completely before reinstalling. Install the new field, or cleaned field, in the housing and fasten it back down. Reattach all wires and slide the armature back in place. Reattach the motor housing back on the demolition hammer.

The caps hold the brushes in place. If a cap is damaged, or broken, it will not be able to hold the brush in place with the correct amount of pressure on the commutator, leading to excessive sparks. To check and replace these caps, remove the end cap on the motor and locate the caps. Remove the caps, separate the brushes and inspect. Replace any broken or damaged caps and install the brushes back in the caps. Install the new caps and reinstall the end cap on the motor.