Multi-Tool: Excessive Sparks From Motor
Check the carbon brushes, armature, field, and switch, if you notice excessive sparks coming from the motor of your multi-tool. If you are having trouble determing which part is causing the problem, read our troubleshooting guide for help with what to look for, and how to repair the part. If you require advice specific to your model, refer to your owner's manual.
There are three tests to use when checking an armature. The first is a continuity test. With the armature removed from the unit, stand it up on a bench. Attach one end of the ohmmeter to the shaft, for ground, and the other to the bar on the commutator. Move the probe to each bar on the commutator, checking all the bars. If the ohmmeter shows a reading on one of these bars, this indicates a short and a bad armature.
The second test is a bar-to-bar test, determining resistance. Attach one probe to the bar on the commutator and the other probe on the bar right beside it. There will be a specific reading for this, depending on the design of the armature. But, most importantly, there is not a large fluctuation here between the values, indicating a fault. If there is an increase in resistance, this will indicate there is a broken, or burned out, wire in the coil. If the resistance drops, the there is a short. Move around the commutator, checking each bar.
The third test is the 180-degree test. Attach the two ends of the ohmmeter on the commutator bars, directly across from each other. There will be a specific set of readings for this, depending on the design of your unit. Once again, what is important is that there is not a large fluctuation in values, which would indicate fault. If there is an increase in resistance, that would indicate a broken, or burnt out, wire. If the resistance drops that would indicate that there is a short. Continue this test on all the bars. If an armature fails any of these tests, it is recommended that you replace it.
Slide the armature into the field. Connect the switch and the circuit board and install into the housing. Reinstall the hold-down screws and the power cable connector. Secure the two halves of the housing back together. Secure the front cap back on and install the collet nut and collet. Reinstall the brushes and caps.
Replace the field if burn marks are present. You can check the condition of the field by performing a couple of tests. Using a multimeter, you...
Replace the field if burn marks are present. You can check the condition of the field by performing a couple of tests. Using a multimeter, you can check the field for continuity. Set the multimeter to the ohmmeter and place a lead on each end of the coil in the field. You will have to perform this test for each coil in the field. If the reading is infinity for one, or more, for the coils, then the field is bad and requires replacement. If there is a major variance between the coils, then the field needs to be replaced. Slide the armature into the field and then connect both the switch and circuit board, installing them in the housing. Reinstall the hold-down screws and the power cable connector. Join the two halves of the housing back together. Screw the front cap back on and reinstall the collet nut. Finally, reinstall the brushes and caps.