Toyota 4Runner manuals

Toyota 4Runner: On-vehicle Inspection

ON-VEHICLE INSPECTION

PROCEDURE

1. INSPECT REFRIGERANT PRESSURE WITH MANIFOLD GAUGE SET

(a) This method uses a manifold gauge set to locate problem areas. Read the manifold gauge pressure when these conditions are established.

Test conditions:

  • Temperature the air inlet is 30 to 35°C (86 to 95°F).
  • Engine is running 1500 rpm.
  • All doors are fully open.
  • Blower speed control switch is set to HI.
  • Air inlet control set to RECIRC.
  • A/C switch is on.

Gauge readings (Reference)


(1) Normally functioning refrigeration system.

Gauge Reading:

Pressure Side

Refrigerant Volume

Low

150 to 250 kPa (1.5 to 2.5 kgf/cm2, 21 to 36 psi)

High

1370 to 1570 kPa (14 to 16 kgf/cm2, 199 to 228 psi)


(2) The A/C system periodically changes between normal and improper function due to moisture in the refrigerant system.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

During operation, pressure on low pressure side cycles between normal and vacuum

Moisture in refrigeration system freezes expansion valve orifice, causing temporary stop of cycle. However, when melted, normal state is restored.

- Dryer is overly saturated

- Moisture in refrigeration system freezes expansion valve orifice and blocks refrigerant circulation

1. Replace cooler dryer

2. Remove moisture from cycle by repeatedly evacuating air

3. Supply appropriate volume of new refrigerant

(3) The A/C system does not function effectively due to insufficient refrigerant.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Pressure low on both low and high pressure sides

- Cooling performance insufficient

Gas leakage from refrigeration system

- Insufficient refrigerant

- Refrigerant leakage

1. Check for gas leakage and repair if necessary

2. Supply appropriate volume of new refrigerant

3. If indicated pressure value close to 0 when connected to gauge, create vacuum after inspecting and repairing location of leakage

(4) The A/C system does not function effectively due to poor circulation of the refrigerant.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Pressure low on both low and high pressure sides

- Frost exists on piping from condenser to A/C unit

Refrigerant flow obstructed by dirt in condenser

Condenser clogged

Replace condenser

(5) The A/C system does not function or functions intermittently because the refrigerant does not circulate.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Vacuum indicated on low pressure side and extremely low pressure indicated on high pressure side

- Frost or condensation seen on piping on both sides of condenser or expansion valve

- Refrigerant flow obstructed by moisture or dirt in refrigeration system

- Refrigerant flow obstructed by gas leakage from expansion valve

Refrigerant does not circulate

1. Check expansion valve refrigerant

2. Clean expansion valve by blowing air

3. Replace condenser

4. Evacuate air and charge appropriate volume of new refrigerant

5. For gas leakage from expansion valve, replace expansion valve

(6) The A/C system does not function effectively due to overcharged refrigerant or insufficient cooling of the condenser.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

Pressure extremely high on both low and high-pressure sides

- Excessive refrigerant

- Cooling performance of condenser insufficient

- Condenser is dirty

- Condenser fan motor is malfunctioning

- Excessive refrigerant

1. Clean condenser

2. Check condenser fan motor operation

3. If 1 and 2 are normal, check amount of refrigerant and supply appropriate volume of refrigerant

(7) The A/C system does not function due to air in the refrigeration system.

CAUTION:

The low-pressure piping may be very hot and cause serious burns.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Pressure extremely high on both low and high-pressure sides

- Low-pressure piping is too hot to touch

Air in refrigeration system

- Air in refrigeration system

- Vacuum purging insufficient

1. Check if compressor oil is dirty or insufficient

2. Evacuate air and charge new refrigerant

(8) The A/C system does not function effectively due to an expansion valve malfunction.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Pressure extremely high on both low and high-pressure sides

- Frost or condensation on piping on low-pressure side

Problem with expansion valve

- Excessive refrigerant in low pressure piping

- Expansion valve open too wide

Replace expansion valve

(9) The A/C system does not function due to a defective compressor.


Symptoms

Probable Cause

Diagnosis

Corrective Actions

- Pressure extremely high on both low and high-pressure sides

- Pressure extremely low on high pressure side

Internal leakage in compressor

- Compression failure

- Leakage from damaged valve or sliding parts broken

Repair or replace compressor

Refrigerant
...

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