PUMP GP-PISTON & GEAR 4348189 - Caterpillar

Tandem-Powered Tractor-ScrapersElectronic switching is now used in transmission control systems of tandem-powered tractor-scrapers. The electronic switches used in these systems are made for low-voltage, current limited electrical circuits only, with many low-current diodes in the sealed case of the switch. The application of any current higher than the design current can permanently damage the diodes and destroy the operation of the switches. The normal voltage of the machine electrical system, plus the output voltage of the 1P3550 and 5P6590 Wiring Harness Tester Groups can cause enough current to damage the electronic switches. For this reason, any tests of the electronic switching system or its components must be made with caution. Check these notes: 1. A 1P3550 or 5P6590 Wiring Harness Tester Group can be used only to test a wiring harness after it is disconnected from the electronic switches and electronic control. DO NOT use the tester to make a system test, to test a transmission switch, or to make a transmission shift test, either on or off the machine.2. Use only test information specifically shown for "Electronic Switching" in later Service Manuals. The "Power Shift Transmission-Testing And Adjusting" modules (sections) and "Schematics" in later Service Manuals for these machines have specific identification for use with "Electronic Switching", and give complete details of correct test procedures. Do not use test procedures for earlier systems which are also shown in the Service Manual for earlier models. Use of test procedures for earlier systems can cause damage to an electronic switching system.3. Use only a multimeter like the 6V3030 or 8S4627 Circuit Continuity Tester to test switches of an electronic switching system. Information to make these tests is also given in the test procedures of later Service Manuals. New test equipment for transmission control systems with electronic switching is under development, and will be available soon. The new equipment will permit more complete tests, including transmission shift tests either on or off the machine. A Special Instruction will also be available soon, with information about the limited use of 1P3550 and 5P6590 Wiring Harness Tester Groups on transmission control systems with electronic switching, and a CAUTION decal transfer, Form Number SEHS7841 for installation on the tester will make reference to the Special Instruction.