EDGE-CUTTING 1187110 - Caterpillar

3304, 3306, 3406, 3408, 3412 Packaged Generator Sets Equipped With SR4 Generators And Type 3 Or Type 4 Control PanelsAn article with the same title was published in the October 17, 1983 Service Magazine. Put a mark through that article, and make a reference to this new article. The schematic and the modification are not correct.
The above units are equipped with automatic start/stop systems. The units are built to start when there is a load demand, to pick up the load, to supply power to the load and to shut down after the load has been removed. This is done without an operator.
There have been reports of failures of the starter motors on these engines. Some of these failures were caused by burned-out run relays and burned-out circuit paths to the run relays. When the run relay or the circuit path to the relay is burned out, no power is supplied to the overcrank timer. This permits the starter motor to remain engaged after the generator set engine is running. The result is a failure of the starter motor.
The new control panels are wired differently to prevent this type of problem. See the October 25, 1982 Service Magazine article, "Improvements To Generator-Mounted Control Panels," and the August 23, 1982 Service Magazine article, "New Time Delay Conversion Groups Available." If desired, a modification can be made to the control panel to supply power to the overcrank timer each time the starter motor is activated. This modification will supply power to the overcrank timer even if the run relay or the circuit path is burned out. The overcrank timer will then disengage the starter motor after 30 seconds. This will prevent damage to the starter motor caused by the starter running with the engine or by the starter motor burning out if the engine doesn't start.
To make this modification, disconnect the wire from the No. 3 pin on the No. 3 contact on the arming relay. Connect this wire to the No. 1 pin on the arming relay. Connect a wire between the No. 32 terminal on the control panel terminal strip and the No. 7 pin on the arming relay. See the illustration.
Locations of terminals, pins and relays where modifications are needed.