Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: On-vehicle Inspection

• Doors are fully open.
• The engine is idling.
• The A/C switch is on.
• The temperature is set to max cool.
• The blower speed is set to high.
• Temperature at the air inlet with recirculate selected is 30 to 35°C (86 to 95°F).

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

   Symptom	Air conditioning system periodically cools and then fails to cool
   Probable Cause	Moisture in air conditioning system freezes at expansion valve orifice, causing refrigerant to temporarily stop circulating
   	After system stops and warms up again, ice melts and normal operation is temporarily restored
   Diagnosis	Cooler dryer (integrated into condenser tank) saturated with moisture
   	Moisture in air conditioning system is freezing at expansion valve orifice and blocking circulation of refrigerant
   Corrective Actions	Replace cooler dryer
   	Remove moisture by repeatedly evacuating air from air conditioning system
   	Recharge air conditioning system with proper amount of new or purified refrigerant

   HINT:

   For the example above, moisture is present in the air conditioning system.

2. Pressure is low on both low and high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively
   	Insufficient cooling performance
   Probable Cause	Refrigerant leaks from air conditioning system
   Diagnosis	Insufficient refrigerant
   	Refrigerant leaking
   Corrective Actions	Check for refrigerant leaks and repair if necessary
   	Recharge air conditioning system with proper amount of new or purified refrigerant
   	If gauges indicate pressure of close to 0, then it is necessary to evacuate air conditioning system after repairing leaks

   HINT:

   For the example above, there is insufficient refrigerant.

3. Pressure is low on both low and high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively
   	Frost exists on pipe from condenser to evaporator unit
   Probable Cause	Refrigerant flow is obstructed by dirt inside pipes of condenser core
   Diagnosis	Condenser is clogged
   Corrective Actions	Replace condenser

   HINT:

   For the example above, there is poor circulation of refrigerant.

4. Vacuum is indicated on low pressure side and very low pressure is indicated on high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively (System may cool occasionally)
   	Frost or condensation is seen on piping on both sides of receiver/dryer or expansion valve
   Probable Cause	Refrigerant flow is obstructed by moisture or dirt in air conditioning system
   	Expansion valve is stuck closed
   Diagnosis	Refrigerant does not circulate
   Corrective Actions	Replace expansion valve
   	Replace condenser
   	Evacuate air conditioning system and recharge with proper amount of new or purified refrigerant

   HINT:

   For the example above, the refrigerant does not circulate.

5. Pressure is too high on both low and high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively
   Probable Cause	Unable to provide sufficient performance due to excessive amount of refrigerant
   	Cooling effectiveness of condenser is insufficient
   Diagnosis	Excessive amount of refrigerant in air conditioning system because excessive refrigerant was added during recharging
   	Cooling effectiveness of condenser is insufficient because condenser fins are clogged or cooling fan is faulty
   Corrective Actions	Clean condenser
   	Check operation of condenser cooling fan
   	If condenser is clean and fan operation is normal, check amount of refrigerant and recharge air conditioning system with proper amount of new or purified refrigerant

   HINT:

   For the example above, the air conditioning system is overcharged or cooling effectiveness of condenser is insufficient.

6. Pressure is too high on both low and high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool
   	The low pressure piping is too hot to touch
   Probable Cause	Air in air conditioning system
   Diagnosis	Air present in air conditioning system
   	Insufficient vacuum purging when evacuating air conditioning system
   Corrective Actions	Replace cooler dryer
   	Check compressor oil to see if it is dirty or insufficient
   	Evacuate air conditioning system and recharge it with new or purified refrigerant

   NOTICE:

   These gauge indications occur when the air conditioning system has been left open and then recharged without evacuating the system.

   HINT:

   For the example above, air is present in the air conditioning system.

7. Pressure is too high on both low and high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively
   	Frost or large amount of condensation on piping on low pressure side
   Probable Cause	Expansion valve may be stuck open or metering refrigerant incorrectly
   Diagnosis	Excessive refrigerant in low pressure piping
   	Expansion valve open too wide
   Corrective Actions	Replace expansion valve

   HINT:

   For the example above, there is an expansion valve malfunction.

8. Pressure is too high on both low and high pressure side or pressure is too low on high pressure side

   *a	LO
   *b	HI

   Symptom	Air conditioning system does not cool effectively
   Probable Cause	Internal leak in compressor
   Diagnosis	Low compression
   	Leak from damaged valve or other compressor component
   Corrective Actions	Replace compressor

   HINT:

   For the example above, there is insufficient compressor compression.

Precaution

PRECAUTION PRECAUTIONS FOR REFRIGERANT HFO-1234yf (R1234yf) (a) Compatibility (1) The parts used in the refrigerant cycle, the compressor oil, etc. of an HFO-1234yf (R1234yf) system are not compatible ...

Replacement

REPLACEMENT PROCEDURE 1. RECOVER REFRIGERANT FROM REFRIGERATION SYSTEM (a) Start the engine. (b) Operate the compressor under the following conditions: Item Condition Operating Time 3 minut ...

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