Two common reasons for motor assembly failure are loss of gear teeth on the worm wheel and wear in the bearing journals in the side plates.
First, the worm wheel gear has been changed to a continuously lubricated bronze gear. An oil saturated felt washer, shown at right, continuously supplies lubrication to the worm and the wheel.
Second, bearing journal wear, where the worm wheel’s shaft rides on the side plate, has been reduced both by choosing a more wear resistant material combination and also adding an oil infused felt washer between the cam and side plate. The shaft is now bronze running a steel journal in the side plate.
These design changes eliminate switch failure requiring motor assembly replacement.
When a motor operated switch operates slowly both mechanically and electrically, one of the ratcheting cams has failed.
Fixing this problem is time consuming and difficult because disassembling the motor mechanism is like disassembling a clock. A better solution is to purchase a new motor mechanism assembly.
When this failure occurs, cams do not grip the shaft. Energy cannot be stored in the springs and the switch will not operate. This failure occurs because of one of two causes.
First, the cam bearings are not gripping the shaft because the cam bearings are mounted in soft aluminum journals. The soft material cannot maintain dimensional tolerances the cams require to properly operate. This failure is prevented by changing the material from aluminum to stainless steel.
Second, the journal is in a boss which is welded to the ratcheting cam. When a weld fails, the cam will not work. When the ratcheting cams are made from stainless steel, the boss is keyed to the ratcheting cam and braised together.