TM  10-3930-638-24&P APPENDIX   F E L E C T R I C A L    A N D    H Y D R A U L I C    D I A G R A MS Section   I.   INTRODUCTION F - 1     G E N E R AL F-2.   DIAGRAMS This appendix contains an electrical diagram and an The hydraulic diagram is located in figures F-3 and F-4 and hydraulic diagram. Also included in this appendix is a the electrical diagram is located in figure F-5. Figure F-3 description of how to use the electrical diagram as an aid shows the hydraulic oil flow when the various controls are to troubleshooting (section 11). Section 111 contains the in the neutral position. Figure F-4 shows the hydraulic oil diagrams  (figures  F-3  through  F-5). flow when the controls are activated. Section   II.   HOW   TO   USE   ELECTRICAL   SCHEMATIC   AS   AN   AID TO   TROUBLESHOOTING F-3.   OVERVIEW a. Figure F-5. your Electrical Diagram. is designed to help  you  understand  the  electrical  circuits  associated  with this vehicle. It is generally referred to as a “schematic” and uses “symbols” to represent real components. It is not drawn to scale (as in a blueprint) nor does the location of the symbols represent actual location of components in the vehicle. It is a simple “picture” of how the circuits and components are connected together. b. To quickly find a malfunction or trouble in the electrical system and repair it requires an understanding of how the system operates and a method for checking it out. “Troubleshooting”  provides  the  “method”  for  check  out procedures and your technical manual (Troubleshooting tables and schematics) provides the “operating principles”. F-4.   TROUBLESHOOTING Troubleshooting  is  the  systematic  (step-by-step)  isolation of a malfunction or trouble to the faulty component, harness connector/wire. It is a guide that helps develop a routine or “way” of finding troubles in any electrical system or circuit. As you become more familiar with this vehicle and gain experience, you will find ways to shorten these procedures and decrease down time. BEFORE you attempt to make any repairs or checks, do the following: a. Find out how the system works under normal condi- tions and how to operate it. b. Make sure the malfunction or trouble reported to you “really” exists. (“Dead batteries” could end up as a "failure to start” because of a faulty neutral start switch or the transmission shift lever not fully engaged in park or neutral.) Try to duplicate the trouble so you can be sure you’re on the right track. c. Check troubleshooting index for most likely cause, then identify the circuit that is malfunctioning. d. Study the electrical schematic to learn which com- ponents, harnesses, or wires could contribute to or cause the malfunction. NOTE Remember, when tracing circuits on the elec- trical schematic, that you should always start at the positive (+) side of the battery. Current will flow outward from that point through the circuits and return to the negative (–) side of the battery by way of ground wires and the vehicle  frame. e. Make necessary tests and checks to isolate circuit or component as outlined in the troubleshooting section of this technical manual. f. Make repairs, if you’re sure. If not, continue to isolate the malfunction, or ask for help from your foreman or  supervisor. g.  After  repairs,  make  sure  everything  has  been  re-con- netted  and  tightened. h. Make operational checks to verify that the system/ circuit is functioning properly again. F-1