MOUNTING GP-CAB 1437239 - Caterpillar

1. Many of the connections between the harnesses, in the area of the cab, are made with rubber plugs. If these connections are not tight, they can be the cause of several problems at one time or they can cause problems which come and go. Make sure the rubber plugs are tight before other tests are done.2. Use the 5P7277 Tester to test a circuit for voltage instead of a VOM (volt-ohm-milliammeter). A VOM may show voltage when there is a bad connection and not enough current.3. Use the 8S4627 Circuit Tester to test circuits without voltage for continuity. The light in the 8S4627 Circuit Tester is dim (not much light) with a 10 ohm resistance in the circuit. It becomes brighter (more light) with less resistance. The 8S4627 Circuit Tester can also be used to test diodes. The point of the tester is positive (+) if the batteries are installed correctly. The Tester light must be dim with the point of the tester connected to the base (anode, positive side) of the diode. It should not be on at all when it is connected in the reverse direction with the point connected to the cathode (negative side) of the diode .
5P7277 VOLTAGE TESTER4. Failure of an electrical component can cause or be caused by the failure of one or more other components. Always find the cause of the failure of an electrical component before making a replacement of the component.
8S4627 CIRCUIT TESTERDiodes
Several silicon diodes are used in the 988B electrical system. The purpose of a diode is to permit the flow of current in one direction but not in the other direction. Diodes are shown on schematics as: The shape of the diode symbol is an indication of the direction that current can flow.The identification of the diodes used in this system can be made from the drawing that follows. The end with the band is the cathode. On the 988B, diodes are used for the purposes that follow:1. Reverse Polarity Protection Make reference to "Starting Circuit" drawing, Figure 57. Diode "D" in the diode assembly #3 is used to prevent the operation of the power key switch if the batteries are installed in the reverse direction by accident. If the power key switch were activated with the batteries in the reverse direction, damage to the entire electrical system would be the result.In this circuit, current is constantly sent through the diode during normal operation. It prevents the flow of current only if the batteries are installed in a reverse direction.2. Isolation Look at Figure 29 Variable Capacity Torque Converter (VCTC) Indicator. These are really two circuits, the lamp circuit at the left and the solenoid circuit at the right. Both are controlled by the 4V3087 Switch. When the Lamp Test Switch is operated, it is to test the indicator light only, not the solenoid. The diode isolates the current flow to the solenoid. It only goes thru the test panel switch to ground. If the test