PTC Heater Circuit

AIR CONDITIONING: AIR CONDITIONING SYSTEM: PTC Heater Circuit
- PTC Heater Circuit

DESCRIPTION

The PTC heater is installed in the radiator in the heater unit and operates when cooling water temperature is low and normal heater effectiveness is insufficient.

The air conditioning amplifier switches the circuit in the PTC relay and operates the PTC heater when the operating conditions (cooling water temperature is below 55°C (131°F), setting temperature is MAX. HOT, air outlet damper position is FOOT or FOOT/DEF, and blower switch is not OFF) are met.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSE (PTC HTR1, PTC HTR3, PTC HTR)

(a) Remove the PTC HTR1 and PTC HTR3 fuses from the engine room No. 4 relay block, and PTC HTR H-fuse from the engine room No. 1 junction block.

(b) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPLACE FUSE
OK -- Continue to next step.

2. CHECK AIR CONDITIONING AMPLIFIER





(a) Remove the air conditioning amplifier with its connectors still connected Removal.

(b) Measure the voltage according to the value(s) in the table below.

Standard voltage:





NG -- REPLACE AIR CONDITIONING AMPLIFIER Removal
OK -- Continue to next step.

3. INSPECT PTC HEATER RELAY (PTC HTR1, PTC HTR3)





(a) Remove the PTC heater relays from the No. 4 relay block.

(b) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPLACE PTC HEATER RELAY
OK -- Continue to next step.

4. CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - PTC HEATER, BATTERY AND BODY GROUND)





(a) Remove the PTC heater relays from the No. 4 relay block.

(b) Disconnect the L40 PTC heater connector.

(c) Measure the resistance and voltage according to the value(s) in the table below.

Standard resistance:





Standard voltage:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

5. INSPECT PTC HEATER





(a) Remove the PTC heater Disassembly.

(b) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPLACE PTC HEATER Removal
OK -- Continue to next step.

6. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - BODY GROUND)





(a) Disconnect the L76 air conditioning amplifier connector.

(b) Measure the resistance according to the value(s) in the table below.

Standard resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR

OK -- REPLACE AIR CONDITIONING AMPLIFIER Removal