TECH BASICS 5 FORD 2G (IAR) CHARGING SYSTEMS Ford introduced the 2G alternator in 1984. The voltage regulator is attached to the rear housing. There are two different wiring schemes used, which depend on whether the vehicle has a charge-light or only a charge-gauge. FIGURE 1 shows the components and wiring for a charge-light system. Gauge-only systems will be discussed in the next section. Here’s a list of the components as shown in FIGURE I and some common problems. You should read this list and familiarize yourself with the parts no matter which system you are troubleshooting. Battery — should be fully charged and load tested before diagnosing any charging problem Starter relay — isn’t part of the charging system, but serves as a connection point for the fusible link and the positive battery cable. Charging system fuse — located in the fuse box. It may also protect other dash warning lights and gauges. bene tebe Fusible link — protects the wire to the alternator BAT terminals and the voltage regulator A terminal. This harness is a common problem area. The fusible link can be bad or it can be corroded away. The connection where the wire branches off to the A terminal of the voltage regulator is also prone to corrosion which can cause low voltage or no voltage at the A terminal. Opening the harness and repairing the connection is the fix here. Ignition switch Resistor — allows current to flow in case of bulb failure. Not used in gauge-only vehicles. Indicator Light — bulb can fail. Not used in gauge-only vehicles. Voltage regulator and plug — Use dielectric grease on all connections. Alternator — be sure to clean corrosion off the grounding areas where the alternator mounts. Rectifier Plug — see section titled “Changing the Rectifier Plug”. ink Be ree Re HE Electric choke — always check the routing of the choke wire. It’s common to find it melted to the exhaust manifold or snagged under a valve cover from the last valve cover gasket change. @®800000 A White/black Black/orange Figure 1 — Components of a typical 2G charging system with a charge-light 02/2003 Copyright © 2003 Wesley S. Grueninger – All Rights Reserved Page 1 r ELH BASICS 95 FORD 2G (IAR) CHARGING SYSTEMS CHARGE-LIGHT SYSTEM – How it Works The system with a charge-light has two stages of operation. T The first stage is KOEO (Key on, Engine off) During KOEO current flows from the battery = through the fuse > through the ignition switch > through the charge-light/resistor > to the voltage regulator J terminal. What’s the resistor for? It’s there as a backup for the charge-light bulb. If the filament in the bulb breaks, current will bypass the bulb and still get to the 7 terminal on the voltage regulator. Without the resistor, a blown charge-light bulb could disable the charging system! As soon as the voltage regulator “sees” current at the J terminal, it directs current from the A terminal to the rotor which causes it to become an electromagnet. KOEO current flow – Regulator grounds the “I” terminal – Regulator uses current from “A” terminal to energize the rotor @80000 Figure 2 – Charge-light system KOEO (key on, engine off) That’s it for KOEO. The charge-light is on and the alternator is energized. It’s time to start it up. The second stage is KOER (Key on, Engine running) As soon as the alternator starts charging, it sends current out the STA terminal. The current leaving the STA terminal is not at full charging-system voltage. On a_ good alternator, it will always measure about one-half the alternator charging voltage. For example, if you measure 14.0 volts across the battery, the STA voltage at the alternator will be approximately 7.0 volts. The STA terminal output serves two purposes. On a carbureted engine with an electric choke, it powers the choke heater element. It also goes to the voltage regulator S terminal. As soon as the voltage regulator senses voltage at the S terminal, it opens the connection between the I terminal and ground, thereby turning off the charge-light. 02/2003 Copyright © 2003 Wesley S. Grueninger – All Rights Reserved KOER current flow – Alternator “STA” terminal produces % voltage output to electric choke heater and regulator “S” terminal. – Regulator opens “I” terminal and charge-light goes out. – Alternator-produced current flows from “BAT” terminals to the battery. – Regulator controls alternator output. @®00000 Figure 3 – Charge-light system KOER (key on, engine running) Page 2 rc L T CH BASICS § FORD 2G (IAR) CHARGING SYSTEMS Gauge-only systems have two stages of operation. The first stage is KOEO (Key on, Engine off) During KOEO current flows from the battery = through the fuse > through the ignition switch > to the voltage regulator S terminal. As soon as the voltage regulator “sees” current at the S terminal, it directs current from the A terminal to the rotor which causes it to become an electromagnet. The voltage regulator J terminal is not used in gauge-only systems. That’s it for KOEO. The alternator is energized. It’s time to start it up. KOEO current flow – Ignition switch sends power to the regulator “S” terminal – Regulator uses current from “A” terminal to energize the rotor @®808000 Figure 4 – Gauge-only system KOEO (key on, engine off) The second stage is KOER (Key on, Engine running) As soon as the alternator starts charging, it sends current out the rectifier plug STA terminal. The current leaving the rectifier plug STA terminal is not full charging-system voltage. On a good alternator, it will always measure about one-half the alternator charging voltage. For example, if you measure 14.0 volts across the battery, the rectifier plug STA voltage at the alternator will be approximately 7.0 volts. The STA terminal output serves only one purpose on gauge-only systems. On a carbureted engine with an electric choke, it powers the choke heater element. It is not used on fuel injected vehicles. 02/2003 Copyright © 2003 Wesley S. Grueninger – All Rights Reserved KOER current flow – Ignition switch sends power to the regulator “S” terminal – Alternator “STA” terminal produces % voltage to the electric choke heater. – Alternator-produced current flows from “BAT” terminals to the battery. – Regulator controls alternator output. | @®008000 Figure 5 – Gauge-only system KOER (key on, engine running) Page 3