03DelcoRemy Diagnostic Manual130004222020

Page 20 NOTE If more than one wire is connected to the alternator output terminal, clamp around ALL these wires. Test NOTE In the following test, alternator should be turning at approximate rated speed. Most heavy duty alternators are rated at 5000 rpm. Check manufacturer’s specifications for specific alternator being tested. 1. If off, start engine and make sure all vehicle electrical loads are turned off. Speed up engine. Turn on and adjust carbon pile until ammeter reads its highest value. Record this reading. 2. Turn off carbon pile and engine. 3. If reading is zero (no output), magnetize the rotor with the alternator hooked up normally. Momentarily connect a jumper lead from the battery positive (+) to the alternator relay (R) or indicator (I) terminal. This procedure applies to both negative and positive ground systems and will restore the normal residual magnetism. 4. Repeat steps 1 and 2. If output is still zero, replace the alternator. 3-32. ALTERNATOR REPLACEMENT. Replace alternator if either of the following conditions exist: 1. Alternator output voltage exceeds 15.5 volts (paragraph 3-30). If alternator has separate regulator, use the appropriate regulator service bulletin to isolate the defect. 2. Alternator output current is not within 10% of alternator rated output (stamped on alternator case). Examples: 30-SI - 105 amps, 26-SI - 85 amps, and 21-SI - 100 amps. 3-33. COMPLETION OF ALL TESTS Make sure that all test instruments have been removed from the vehicle and that the vehicle wiring, if altered, has been returned to the operational state. DP-1028 CARBON PILE FIGURE 3-10. Amperage Output Test