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Home >> Lexus >> 1995 >> SC 400 >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> A/C-Heater System >> Trouble Shooting >> Code 21: - Solar Sensor Circuit >> Sensor Resistance Test
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Sensor Resistance Test

  1. Remove solar sensor. See SOLAR SENSOR R & I  under REMOVAL & INSTALLATION. Unplug solar sensor harness connector. Cover sensor with cloth. Connect positive lead of ohmmeter to sensor terminal No. 2. Connect negative lead of ohmmeter to sensor terminal No. 1. Record sensor resistance. Remove cloth. Subject sensor to bright light, and measure resistance between sensor terminals.
  2. If resistance is not as specified, replace sensor. See SOLAR SENSOR RESISTANCE SPECIFICATIONS  table. If resistance is within specification, inspect wiring harness and connectors between sensor and A/C-heater control panel. Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good A/C-heater control panel, then retest system.
SOLAR SENSOR RESISTANCE SPECIFICATIONS

Condition (1) Ohms
Sensor Covered By Cloth No Continuity
Sensor Subjected To Bright Light About 4000
(1) As light intensity increases, resistance should decrease.
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