Multi-Tool: Lacks Power
If your multi-tool lacks power, then you aren't getting the most out of your tool. Our experts have narrowed down the most common parts associated with this symptom, and have provided instructions on how to inspect the part for signs of malfunction, and how to fix it quickly and accurately. The parts we suggest to inspect are the carbon brush, switch, power cord, armature and bearing. Don't waste money on hiring someone else to do a repair that you can easily do yourself. Refer to your owner's manual for detailed instructions for your model.
Separate the motor from the switch and circuit board. Slide the armature free from the field. Clean the armature only with electrical contact cleaner and then wipe dry. Inspect the armature for burn marks and melted insulation on the windings. If there are burn marks, or melted insulation, on...
Separate the motor from the switch and circuit board. Slide the armature free from the field. Clean the armature only with electrical contact cleaner and then wipe dry. Inspect the armature for burn marks and melted insulation on the windings. If there are burn marks, or melted insulation, on the armature, you need to replace it. You can test the armature to check its condition.
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 the bars, this will indicate a short and a bad armature.
The second test is a bar-to-bar test, determining resistance. Attach one probe to a 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, which would indicate a fault. If there is an increase in resistance, this will indicate a broken, or burned out, wire in the coil. If the resistance drops, then 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. Again, what is most important is that there is not a large fluctuation in values, which would indicate a 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 and connect the switch and the circuit board then reinstall it into the housing. Secure the motor and power cable connector in the housing. Rejoin the two halves of the housing back together. Reinstall the front cap back, the collet nut and collet. Reinstall the brushes and caps.
To check the bearing, remove the collet nut, the collet and unscrew the front cap from the multi tool. Remove the brush caps, along with the brushes. Take out the screws and separate the two halves of the housing. Remove the power cable connector. Remove the screws securing the motor assembly and remove the motor. Separate the motor from the switch and slide the armature out of the field. Remove the rubber ring on the lower bearing....
To check the bearing, remove the collet nut, the collet and unscrew the front cap from the multi tool. Remove the brush caps, along with the brushes. Take out the screws and separate the two halves of the housing. Remove the power cable connector. Remove the screws securing the motor assembly and remove the motor. Separate the motor from the switch and slide the armature out of the field. Remove the rubber ring on the lower bearing. Spin the bearings – looking for a seized, or partially-seized, bearing. Bearings should spin freely, with no noise. Also, if the bearing spins rough, makes noise or has play, replace it.
To replace the lower bearing, use a bearing puller. Wipe the shaft clean and install a new bearing on the shaft, tapping it in place with a hammer and a socket. To avoid damage to the bearing, only use a socket that contacts the bearings inner race. Reinstall the rubber ring.
To replace the upper bearing, use a bearing separator to remove it. Place the separator under the bearing and then lay the separator on an open vice and tap the shaft free of the bearing. Use a mallet, or a brass hammer, to avoid damaging the armature shaft. Hang on to the armature shaft so it does drop on the floor.
Clean the shaft and install the new bearing by placing a socket on the bearings inner race, tapping it in place with a hammer. Slide the armature back in the field. Reconnect the switch and the circuit board and reinstall back in the housing. Secure the motor in place with the power cable connector. Reconnect the housing back together and screw the front cap back on and install the collet and the collet nut. Reinstall the brushes and caps.