movement in the dashpot; if it sticks, the dashpot must be overhauled. Lubricate sector bearings. Make
sure that the voltage regulator is set to manufacturer's specifications. Poor regulation can result from dirt
in the dashpot, commutators and sectors, main shaft bearings, or actuating shaft bearings.
A relay voltage regulator is serviced by checking the following: contacts for wear; current coil
connections for tightness; electrical connections for tightness and good contact; and coils and resistors
for burns and discoloration. Adjustments should not be made unless detailed instructions for the type of
A commutator load regulator, shown in figure 2.16, has few moving parts. Consequently, it is
easy to keep in service and seldom needs attention except for cleaning. Piping connections must be kept
tight to prevent oil leaks and entry of air into the system. If pipes leak, replace the oil seals in the
operating cylinder or motor shaft. Load regulator timing is controlled by the flow of oil through the pilot
valve, item 1 in figure 2.16, to or from the regulator.
Remove the reverser to dismantle, clean, lubricate, and repair it. Renew piston packing; examine
pinions and racks for wear; clean and test magnet valves; renew or build up and remachine contact
segments; check and adjust contact tension and interlocks; inspect stationary contacts, shunts, and
springs and replace if necessary. Some of these parts of the reverser are pictured in figure 2.17.
At intervals, the valve unit should be disassembled to permit cleaning, checking, and replacing
worn valve parts. To disassemble, first remove the cover. The pole plate may be lifted off and the valve
stem pulled. Taking off the large nut at the bottom allows the removal of the needle valve and spring.
A valve may stick or leak because of a deposit of dirt and good operation may be restored by
washing with a cleaner. If the valve still leaks, the seats are probably scored and it will be necessary to
grind them with a fine grinding compound.
a. Testing valves for leaks. To test the lower valve seat for leaks, cover the air ports in the side
of the magnet valve housing