A damaged power cord is also a safety hazard as it can harm you and cause a fire. Inspect your power cord for cuts, frays, burn marks or anything else out of the ordinary. If the power cord becomes damaged, in any way, it may not be able to conduct the flow of electricity needed. The power cord supplies power to the tool. Screw the front cap back on and reinstall the collet nut, followed by the brushes and caps. Rejoin the two halves of the housing back together. Reinstall the screws to secure it in place and reinstall the power cable connector. Connect the switch and the circuit board and place the assembly in the housing. If there is a major variance between the coils, then the field needs to be replaced. If the reading is infinity for one, or more, of the coils, then the field is bad and requires replacement. You will have to perform this test for each coil in the field. Set the multimeter to an ohmmeter and place a lead on each end of the coil in the field. Using a multimeter, you can check the field for continuity. You can check the condition of the field by performing a couple of tests. Replace the field, if any of this is present. Inspect the field for burn marks and melted insulation. Slide the armature out of the field and then clean the field with electrical contact cleaner and wipe dry. Lift out the motor and separate the motor from the switch and circuit board. Remove the power cable connector and then all of the screws securing the motor and cable connector. Take out the housing screws and separate the two halves of the housing. To inspect the field for damage, such as burn marks and melted insulation, and to perform tests, you will need to take apart the multi tool to access it.īegin by removing the collet nut, collet and front cap. The field is placed around the armature and the two, together, make up the motor. The field is an electromagnet used to generate a magnetic field in an electro-magnetic machine.

Reassemble the housing back together and reinstall the front cap, the collet nut and collet, followed by the brushes and caps. Reinstall the hold-down screws and the power cable connector. Connect the switch and the circuit board to the motor and reinstall the motor assembly into the housing. If an armature fails any of these test, it is recommended that you replace it. If the resistance drops, that would indicate there is a short. If there is an increase in resistance, that would indicate a broken, or burnt out, wire. Again, what is most important is that there is not a large fluctuation in values, which would indicate a fault. There will be a specific set of readings for this, depending on the design of your unit. Attach the two ends of the ohmmeter on the commutator bars, directly across from each other. Move around the commutator, checking each bar.

If the resistance drops, then there is a short. If there is an increase in resistance, this will indicate there is a broken, or burned out, wire in the coil. But, most importantly, there is not a large fluctuation here between the values, indicating a fault. There will be a specific reading for this, depending on the design of the armature. Attach one probe to the bar on the commutator and the other probe on the bar right beside it. The second test is a bar-to-bar test, determining resistance. If the ohmmeter shows a reading on one of the bars, this will indicate a short and a bad armature. Move the probe to each bar on the commutator, checking all the bars. Attach one end of the ohmmeter to the shaft, for ground, and the other to the bar on the commutator. With the armature removed from the unit, stand it up on a bench. There are also three tests you can do to check the condition of the armature. Replace the armature, if these signs are present. Inspect the armature for burn marks and melted insulation on the winding. Clean the armature with electrical contact cleaner and wipe dry. Pull out the motor and separate it from the switch and circuit board and then slide the armature out of the field. Separate the two halves of the housing and then take out the power cable connectors and screws holding down the motor assembly. Remove the brush caps on the side and take out the brushes from the housing. Remove the collet nut, the collet and the front cap.

To check the condition of the armature, and to perform a few tests, you will need to remove the armature from the multi tool. If your multi tool will not power up, it could be cause by a defective armature. The armature, located inside the field, is the power-producing part of the motor and the only moving part of the motor.

Craftsman oscillating multi tool