Pole Saw: Won't Start

The armature is the rotating part of an electric motor, consisting of wires wound around two or more poles of an iron core. The armature has a commutator, which is located on its shaft with the brushes. The commutator acts as a switch for the electromagnet, flipping the flow of electrons, which causes the armature to rotate. To check the armature, remove the drive sprocket cover, then remove the bar and chain from the unit. Remove the E-clip on drive sprocket and remove the clip and sprocket. Remove the screws holding the two halves of the case together. Locate the armature inside the unit and remove it, being careful not to let the springs or the brushes fly out. 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. Attach an ohmmeter to the two ends of the commutator to measure the resistance of the windings. The reading number is not important as you move it around the commutator. You are looking for consistency in the reading, indicating all the windings are good. If it varies radically, reading a zero or open circuit, then the armature is not good. Another test is attaching the ohmmeter on each bar, adjacent to each other on the commutator. You are looking for a constant reading. If the ohmmeter reads a zero or open circuit, that indicates a bad armature. The last test is a bar to ground test, which is done by placing one lead of the ohmmeter to the tip of the shaft of the armature; attach the other end to the commutator. If the armature is bad, install a new one. Rejoin the two halves of the unit back together. Install the drive sprocket and E-clip, bar, and chain. Make sure the chain is installed around the drive sprocket. Install the cover and hand tighten the nut. You may have to rotate the adjuster screw counter clockwise to properly align the tensioner into the hole in the chain bar. Adjust the tension on the chain by turning the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Tighten down the nut on the cover and recheck tension on the chain as it may have changed after the cover was tightened.

The brushes transfer the electricity from outside the motor to the spinning winding in the center of the motor. These brushes undergo a lot of friction and wear down over time. Remove the drive sprocket cover, then remove the bar and chain from the unit. Remove the E-clip, clip, and sprocket. Remove the screws holding the two halves of the case together and separate. Locate the brushes on the commutator and check for wear. If they look worn down, replace them. Remove the brushes from the unit, being careful not to lose the springs. Disconnect the electrical contact. Install new brushes with the spring and re-attach the electrical contact. Re-assemble the two halves of the unit. Re-install the drive sprocket and E-clip, bar, and chain. Make sure the chain is installed around the drive sprocket. Install the cover and hand-tighten the nut. You may have to rotate the adjuster screw counter clockwise to properly align the tensioner into the hole in the chain bar. Then adjust the tension on the chain by turning the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Tighten down the nut on the cover and recheck tension on the chain as it may have changed after the cover was tightened.

Check the power cord for damage that may disrupt electrical flow to the motor. Check for cuts in the cord or fraying; replace the cord if it is damaged. To replace it, first remove the drive sprocket cover then remove the bar and chain. Remove the E-clip and the drive sprocket. Remove all the screws securing the two halves together and separate. Locate the power cord and check the internal electrical connections. Make sure they are attached and secured tight. If the wires are disconnected, reattach if possible. To check the cord for continuity, disconnect it and remove it from the unit. Attach the ends together, then use an ohmmeter on the plug end to check the continuity. If the ohmmeter reads infinity, the power cord is bad and you will need to replace it. Once replaced, rejoin the two halves together. Re-install the drive sprocket with the E-clip, bar, and chain with the chain installed around the drive sprocket. Install the cover and hand tighten the nut. You may have to rotate the adjuster screw counter clockwise to properly align the tensioner into the hole in the chain bar. Adjust the tension on the chain by turning the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Tighten down the nut on the cover and recheck tension on the chain as it may have changed after the cover was tightened.

The switch provides power to the motor on demand. If the unit will not turn on, chances are you have a bad switch. Remove the drive sprocket cover. Remove the E-clip and the drive sprocket. Remove all the screws securing the two halves together. Locate the switch, disconnect it, and remove it from the unit. Attach an ohmmeter to the ends of the switch. Turn the switch on and off. The ohmmeter should read zero then infinity. If the readings do not change, install a new switch. Rejoin the two halves and install the drive sprocket with the E-clip and bar back to the pole saw. Re-install the chain around the drive sprocket. Install the drive sprocket cover and hand tighten the nut. You may have to rotate the adjuster screw counter clockwise to properly align the tensioner into the hole in the chain bar. Adjust the tension on the chain by turning the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Do a final tighten down on the cover nut and recheck tension on the chain, as it may have changed after the cover was tightened.

Retaining rings are designed to fasten components onto the electric motor shaft. To check if a retaining ring has broken off the shaft, you will have to inspect the inside. Try shaking the unit; you may hear something rattling around inside which is a good indicator the ring is loose. Remove the drive sprocket cover, then slide the bar and chain off the unit. Remove the E-clip and sprocket. Separate the two halves of the unit and locate the armature. Inspect the shaft for any missing retaining rings. You should see a broken retaining ring inside the unit. If you do have a broken retainer ring, remove the brushes carefully, making sure the brush springs do not fly off. Remove the armature and install a new retaining ring on the groove located on the armature shaft, making sure it is secure. Re-install the armature and the brushes with the springs, and join the two halves of the unit back together. Re-attach the drive sprocket, with the E-clip and bar, back to the pole saw. Re-install the chain around the drive sprocket. Install the bar cover with the nut, hand tightened. You may have to rotate the adjuster screw counter clockwise to properly align the tensioner into the hole in the chain bar. Adjust the tension on the chain by turning the adjuster screw clockwise. The chain should be tight enough to rotate with one hand and the drive links should not come out of the bar nose. Do a final tighten down on the cover nut and recheck the chain tension, as it may have changed after the cover was tightened.