03DelcoRemy Diagnostic Manual130004222020

Page 2 1-9. BATTERIES. Batteries are perishable devices that wear out at some point in time. With use, they deteriorate and eventually become incapable of performing their important job. In addition, new batteries may become discharged for various reasons. Neither worn out nor discharged batteries can supply the power necessary for cranking. Thus, the battery check becomes the starting point for diagnosing electrical system problems. 1-10. SUBCIRCUITS. Because of vibration, corrosion, temperature changes or damage, the performance of wiring, connections and secondary components as well as the function of the starter and alternator can deteriorate. This, in turn, can cause malfunctions within the starting and charging systems. For the purpose of testing, wiring and components are divided into four circuits that must be tested. These are: 1. Cranking Circuit. This consists of the large cables that carry the high starter current. Excessive loss here causes slow cranking speeds, especially in cold weather. Inability to start from slow cranking can lead to starter damage if the starter is cranked over 30 seconds. Deeply discharged or worn-out batteries also can cause the same problem. 2. Solenoid Circuit. This consists of the wiring from the battery, through a push button or magnetic switch, to the S terminal of the starter solenoid, and back to the battery. Excessive loss here can cause the solenoid to shift in and out (chatter), resulting in a no-start condition. This can cause a damaged contact disc and terminals of the starter solenoid. Deeply discharged batteries also can cause this problem. 3. Magnetic Switch Circuit or IMS (when the magnetic switch is used). This consists of the wiring from the battery, through a key switch and/or start button, to the coil of the magnetic switch, and back to the battery. Excessive loss here can cause a “no start” complaint. 4. Charging Circuit. This consists of the wiring between the alternator and the battery and back to the alternator. Excessive loss here can cause the batteries to not charge properly. As noted above, discharged batteries will cause other problems. 1-11. SEQUENCE OF PROCEDURES. It is important that these procedures be followed in the exact sequence specified. Batteries, wiring and connections should be checked and corrected to the specifications given. If cranking problems still occur, then connecting cables should be checked before replacing the starter with a known good unit. Similarly, in the charging circuit, the batteries, wiring and connections should be thoroughly checked and corrected to the specifications given. Only then should the alternator be checked and replaced if necessary. 1-12. ELECTRICAL FUNDAMENTALS 1-13. TERMS AND DEFINITIONS. The following are electrical terms and definitions used in this manual: 1. Voltage. Voltage is the electrical pressure or force that causes current or electrons to flow through a conductor. The voltage also can be described as the difference in electrical pressure between two points in a circuit. This electrical force or pressure is measured in volts. 2. Current. Electrical current is the flow or movement of electrons in a conductor. This movement can be compared to the flow of water through a pipe. Without pressure (voltage), the current will not flow. Electrical flow is measured in amperes, most often abbreviated as amps. 3. Resistance. Resistance is the opposition to current flow. For a given electrical pressure (voltage), resistance decreases current flow. This can be detected by voltage loss or drops in the electrical circuit. Electrical resistance is measured in ohms. 4. Magnetic Field.When electrical current flows through a conductor, a magnetic field is produced around the conductor. By measuring the strength of this magnetic field, it is possible to determine the amount of the current flow or amperage. This principle is the basis for the function of the clamp-on or induction type ammeter. 1-14. MEASURING VOLTAGE WITH THE VOLTMETER. The voltmeter is used to measure electrical pressure or voltage. The unit of measure is the volt. Voltmeters are always connected across (in parallel with) a part of the electrical circuit (See Figures 1-6 and 1-7). The voltmeter measures the difference in electrical potential or pressure between the points where the voltmeter is attached. 1-15. VOLTMETER SELECTION. Voltmeters for the purposes described in this manual are DC instruments with a range as follows: 1. Low scale: 0-3 volts 2. 12-volt vehicles: 0-16volts 3. 24-volt vehicles: 0-32volts MAGNETIC FIELD CURRENT DP-1005