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Last Modified: 11-27-2007 1.6 J
Service Category: Vehicle Interior Section: Heating/Air Conditioning
Model Year: 2008 Model: LX570 Doc ID: RM000001GFJ00IX
Title: HEATING / AIR CONDITIONING: AIR CONDITIONING SYSTEM: DESCRIPTION (2008 LX570)

PTC Heater Circuit

DESCRIPTION

PTC heater relays are closed in accordance with signals from the air conditioning amplifier assembly and power is supplied to the quick heater assembly installed on the radiator heater unit.

WIRING DIAGRAM

INSPECTION PROCEDURE

PROCEDURE

1.

INSPECT PTC HEATER RELAY (PTC HTR1)


(a) Remove the PTC HTR1 relay from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

Battery voltage is not applied between terminals 1 and 2

10 kΩ or higher

Battery voltage is applied to terminals 1 and 2

Below 1 Ω
OK

2.

INSPECT PTC HEATER RELAY (PTC HTR2)


(a) Remove the PTC HTR2 relay from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

Battery voltage is not applied between terminals 1 and 2

10 kΩ or higher

Battery voltage is applied to terminals 1 and 2

Below 1 Ω
OK

3.

INSPECT PTC HEATER RELAY (PTC HTR3)


(a) Remove the PTC HTR3 relay from the engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

Battery voltage is not applied between terminals 1 and 2

10 kΩ or higher

Battery voltage is applied to terminals 1 and 2

Below 1 Ω
OK

4.

CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY


(a) Remove the air conditioning amplifier assembly with its connectors still connected HEATING / AIR CONDITIONING: AIR CONDITIONING AMPLIFIER: REMOVAL (2008 LX570) .

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

E36-27 (PTC1) - Body ground
  • Engine switch on (IG)
  • Temperature setting: Hi
  • Outside temperature: 10°C (50°F) or less
  • Engine coolant temperature: 73°C (163.4°F) or less
  • Blower switch on

11 to 14 V

E36-26 (PTC2) - Body ground

E36-35 (PTC3) - Body ground
OK

5.

CHECK HARNESS AND CONNECTOR (PTC HEATER RELAY - QUICK HEATER)


(a) Remove the PTC heater relays from the engine room relay block.

(b) Disconnect the E33 quick heater assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

PTC HTR2 terminal 3 - E33-1 (B)

Always

Below 1 Ω

PTC HTR1 terminal 3 - E33-2 (B)

PTC HTR3 terminal 3 - E33-3 (B)

PTC HTR2 terminal 3 - Body ground

Always

10 kΩ or higher

PTC HTR1 terminal 3 - Body ground

PTC HTR3 terminal 3 - Body ground
OK

6.

INSPECT QUICK HEATER ASSEMBLY


(a) Disconnect the E33 and E34 quick heater assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

E33-1 (B) - E34-1 (E)

Always

Below 1 kΩ

E33-2 (B) - E34-1 (E)

E33-3 (B) - E34-2 (E)
OK

7.

CHECK HARNESS AND CONNECTOR (QUICK HEATER - BODY GROUND)

(a) Disconnect the E34 quick heater assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

E34-1 (E) - Body ground

Always

Below 1 Ω

E34-2 (E) - Body ground
OK

8.

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


(a) Disconnect the E36 amplifier connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

E36-27 (PTC1) - Body ground

Always

Below 200 Ω

E36-26 (PTC2) - Body ground

E36-35 (PTC3) - Body ground
OK