TM  10-3930-638-24&P 2-22.   CHARGING   SYSTEM   TROUBLESHOOTING   (cont) MALFUNCTION TEST OR INSPECTION CORRECTIVE  ACTION 1. ABNORMAL ALTERNATOR LIGHT OPERATION (cont) STEP  1.  (cont) b. If ALTERNATOR light is on, grasp and pull connector from alternator terminals 1 and 2. If the ALTERNATOR light goes out, replace the alternator (para 2-26). If the light stays on, check for a short between these wires, then install connector on alternator terminals 1 and 2. Step 2. Place IGNITION switch to ON with engine stopped. ALTERNATOR light should be on. With engine running, ALTERNATOR light should be off. a. If ALTERNATOR light is off with engine stopped, or on with engine running, check for an open circuit between alternator terminal l and ALTERNATOR light. Use an ohmmeter to check diode and 40 ohm resistor in ALTERNATOR light circuit. b. If circuit tests are satisfactory, troubleshoot alternator (MALFUNCTION 2 below). 2. ALTERNATOR OUTPUT LOW, UNSTEADY OR ZERO Step 1. Turn IGNITION switch to ON and alternately connect voltmeter leads from ground to alternator terminal 1, terminal 2 and B terminal. a. If voltmeter indicates 24 Vdc at all  three  terminals,  proceed  to step  2. b. If voltmeter does not indicate 24 Vdc at one or more terminals, check for an open circuit between  battery  positive  post and  affected  alternator terminal. Step 2. Disconnect battery ground cable and connect  an  ammeter  between alternator B terminal and starter relay terminal 3. Reconnect  battery  ground  cable,  and connect a carbon pile across batteries. Turn all vehicle lights on to increase load on batteries, and operate engine at 1800 rpm. a. If ammeter indicates 27 to 47 amperes, but ALTERNATOR light stays on, check for open circuit from alternator terminal 1 in wiring, diode, and 40 ohm resistor. b. If ammeter does not indicate 27 to 47 amperes, replace alternator (para 2-26). 2-104