LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Honda >> 1990 >> Prelude 2.0 S, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests - CARBURETED >> A/C Switch Signal >> Signal Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Signal Testing

  1. Connect ECU Test Harness (07LAJ-PT30100 ) between ECU and ECU connector. See Figure . Disconnect "D" connector from main wire harness only, not ECU. Turn ignition switch to ON position. DO NOT  start engine. Measure voltage between terminal D6 (positive) and terminal A26 (negative). See Figure . If battery voltage is present, go to step 3). If battery voltage is not present, go to next step.
  2. Substitute a known good ECU and recheck voltage between terminals D6 and A26. If voltage is now available, replace original ECU.
  3. Reconnect "D" connector to main wire harness. Place a jumper wire between terminals A19 and A26. See Figure . If A/C system operates, go to step 4). If A/C system does not operate, connect Red/Blue terminal of 4-pin connector on A/C clutch relay to chassis ground. If A/C system now operates, repair open or short in Red/Blue wire between terminal A19 and compressor control unit. If A/C system still does not operate, A/C system may be faulty.
  4. Start engine. Turn blower switch on. Turn A/C switch on. If A/C system does not operate, A/C system may be faulty. If A/C system operates, measure voltage between terminals D6 (positive) and A26 (negative). See Figure . If voltage is below one volt, A/C signal is okay. If voltage is not below one volt, repair open or short in Red/Green wire between ECU terminal D6 and A/C switch.
scientia non olet · About LEMON Manuals