GUARD 2T1151 - Caterpillar

Troubleshooting Methods
1. The connections between harnesses are made with screw together "Cannon" connectors. Make sure the pins are clean and that there are no broken pins. Also make sure that the connectors are fastened together tightly.2. Use a 5P7277 Voltage Tester or a 6V3030 Multimeter to test a circuit for voltage.3. Use an 8S4627 Circuit Tester or a 6V3030 Multimeter 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 anode of the diode . It must not be on at all when it is connected in the reverse direction with the point connected to the cathode of the diode . The 6V3030 has a special scale to test diodes.4. Failure of an electrical component can cause or be caused by the failure of one or more other components. Always find the cause of failure of an electrical component before making a replacement.
5P7277 VOLTAGE TESTER
8S4627 CIRCUIT (CONTINUITY) TESTER
6V3030 DIGITAL MULTIMETERBlock Diagram
The block diagram of the electrical system shows the flow of electricity to the different parts of the system. It does not show all components, wires and connections. The block diagram shows which components work together.The fuses shown in the block diagram are on a fuse panel under the left hand dash. There is a panel on the front of the machine that can be removed to give access to the fuse panel.The dashed (broken) lines in the block diagram are an indication of a control connection, for example a switch that activates a relay.Tractor Scraper Codes And Abbreviations
Use the table that follows for identification of wire and connector colors in the schematics.Two colors divided by a line are an indication of a wire with a stripe (one color with a line along it of another color). R/LT GR is a red wire with a light green stripe. All connections between harnesses on the 639D, other than single wire connections, are made with military-type "Cannon" connectors (multiple pin connector in a metal housing, with a metal ring around it that screws on to the mating connector to hold them together). Connection A between the cab and engine harnesses is made with 23 pin connectors. Connection B between the other cab and engine harnesses is made with 16 pin connectors, and all of the rest of the machine harness connections between the tractor and scraper (C, D, and E) are also made with 16 pin connectors. All of the transmission harness connections are made with 10 pin connectors. The connection to the transmission electronic shifting control is a 30 pin connection.The identification of the connectors is shown in the example. The letter