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Home >> Toyota >> 2019 >> Highlander Limited, FWD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Air Conditioning System (Manual A/C) - Diagnostic Codes & Circuit Tests - (Except Hybrid) >> AIR CONDITIONING SYSTEM (for Manual Air Conditioning System) >> Circuit Tests >> PTC Heater Circuit [12/2013 - 11/2016] >> Description

PTC Heater Circuit [12/2013 - 11/2016]: Description

The air conditioning amplifier assembly sends operation signals to the PTC heater relays when the quick heater assembly operation conditions are met. Based on the signals from the air conditioning amplifier assembly, the PTC heater relays turn on, and power is supplied to the quick heater assembly installed in the air conditioning radiator assembly.

QUICK HEATER ASSEMBLY OPERATION CONDITION

Control ECU Condition
Air Conditioning Amplifier Assembly Engine running
Blower switch: on
Temperature setting: MAX HOT
Light control switch assembly off
  • Engine coolant temperature: 65°C (149°F) or lower (3 PTC heater relays operating)
  • Engine coolant temperature: 70°C (158°F) or lower (2 PTC heater relays operating)
  • Engine coolant temperature: 75°C (167°F) or lower (1 PTC heater relay operating)
Ambient temperature: 10°C (50°F) or lower