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 on the driver and passenger's FOOT sides 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 in not OFF) are met.

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT FUSE (PS HTR, PTC HTR1, PTC HTR2, GAUGE)
(a) Remove the PS HTR H-fuse, PTC HTR1 and PTC HTR2 fuses from the engine room junction block.
(b) Remove the GAUGE fuse from the driver side junction block.
(c) Measure the resistance of the fuses.
Standard resistance:
Below 1 Ohms
NG -- REPLACE FUSE
OK -- Continue to next step.

2. INSPECT PTC HEATER RELAY (Marking: PS HTR, PTC HTR 1, PTC HTR 2)




(a) Remove the PS HTR, PTC HTR 1 and PTC HTR 2 heater relays from the engine room No. 2 relay block.
(b) Measure the resistance of the relays.
Standard resistance:






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

3. CHECK WIRE HARNESS (AIR CONDITIONING AMPLIFIER - BATTERY)




(a) Disconnect the A7 air conditioning amplifier connector.
(b) Measure the voltage of the wire harness side connector.
Standard voltage:






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

4. CHECK AIR CONDITIONING AMPLIFIER (PTC, HT-1, HT-2, VOLTAGE)




(a) Connect the connectors.
(b) Measure the voltage of the connector.
Standard voltage:





HINT:
- PTC operation may stop when the electric load on the vehicle is high. Perform the inspection under conditions with low electric load (such as with headlights turned OFF).
- Since the 2 PTC heaters are gradually turned to the ON position, perform the inspection 30 seconds after the blower switch is turned to the LO position.

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

5. INSPECT PTC HEATER




(a) Disconnect the connector from the PTC heater.
(b) Check the continuity between each terminal.
Standard resistance:






NG -- REPLACE PTC HEATER
OK -- REPAIR OR REPLACE HARNESS AND CONNECTOR