Alternator FR Signal Test

Fig. 23 System checker harness terminal identification:

1987-88 Accord & 1988 Prelude
1. Connect system checker harness between between ECU and harness connectors, Fig. 23, but disconnect B connector from main harness only, not the ECU.
2. Turn ignition on and measure voltage between terminals B14 (+) and A18 (-). If reading is not approximately 5 volts, replace ECU and retest. If reading is approximately 5 volts, original ECU is defective.
3. Turn ignition off and reconnect B connector to main harness.
4. Start engine and run until it reaches normal operating temperature.
5. Measure voltage between terminals B14 (+) and A18 ( - ) while turning headlamps and defogger on and off. Voltage reading should decrease when accessories are switched on system is satisfactory.
6. If voltage reading does not decrease when accessories are switched on, stop engine and disconnect test harness B connector from ECU only, not from main harness.
7. Disconnect battery ground cable and check continuity between tester harness terminal B14, Fig. 23, and body ground. If continuity exists, proceed to step 8; if no continuity exists, proceed as follows:
a. Disconnect green connector from alternator and connect red/white (Accord) or white/red (Prelude) wire to body ground, then check for continuity between test harness terminal B14 and ground.
b. If continuity does not exist, repair open in red/white (Accord) or white/red (Prelude) wire between ECU and alternator. If continuity exists, repair alternator.
8. Disconnect green connector from alternator and check for continuity between terminal B14 in check connector, Fig. 23, and body ground. If continuity exists, repair short in white/red wire between ECU and alternator. If no continuity exists, repair alternator.