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Home › Lexus › 2000 › LS 400 › Repair and Diagnosis › Heating, Ventilation & A/C (HVAC) › HVAC Control Systems › Automatic A/C-Heater Systems › System Tests › Back-Up Power Source Circuit

Back-Up Power Source Circuit

  1. Remove A/C-heater control assembly, leaving harness connectors connected. See A/C-HEATER CONTROL ASSEMBLY  under REMOVAL & INSTALLATION. Turn ignition on. Backprobe between terminal A21-1 (White/Red wire) of A/C-heater control assembly connector and ground. See Figure.
  2. If battery voltage exists, no problem is indicated at this time. If battery voltage does not exist, inspect A/C fuse (7.5-amp). Fuse is located in instrument panel fuse block. If fuse is okay, inspect wiring harness between A/C-heater control assembly and battery. Repair wiring as necessary.
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