Low Pressure Sensor Circuit

DESCRIPTION

The low pressure sensor reduces the capacity of the compressor when the compressor is operating at high speed. This sensor monitors the pressure on the low pressure side at terminal CUT+ and sends a signal to terminal PSW of the A/C amplifier, which increases the accuracy of compressor control.

WIRING DIAGRAM

INSPECTION PROCEDURE

1. CHECK REFRIGERANT PRESSURE

1. Check the sight glass of the cooler unit refrigerant liquid pipe.

   1. Prepare the vehicle according to the chart below.

      Item	Condition
      Vehicle Doors	Fully open
      Temperature Setting	MAX COLD
      Blower Speed	HI
      A/C	ON

   2. Compare the sight glass to the following chart.

      Item	Symptom	Amount of Refrigerant	Corrective Actions
      1	Bubbles visible	Insufficient*	Check for gas leakage and repair if necessary Add refrigerant until bubbles disappear
      2	No bubbles visible	Empty, insufficient, or excessive	Refer to 3 and 4
      3	No temperature difference between compressor inlet and outlet	Empty or nearly empty	Check for gas leakage with gas leak detector and repair if necessary Evacuate A/C system and recharge with proper amount of refrigerant
      4	Considerable temperature difference between compressor inlet and outlet	Proper or excessive	Refer to 5 and 6
      5	Immediately after air conditioning is turned OFF, refrigerant clears	Excessive	Recover refrigerant Evacuate A/C system and recharge with proper amount of refrigerant
      6	Immediately after air conditioning is turned OFF, refrigerant foams and then becomes clear	Proper	-

      1. ^*: Bubbles in the sight glass with the vehicle interior temperature above 35°C (95°F) can be considered normal if cooling is sufficient.
         

NG	CHARGE REFRIGERANT

OK

2. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER - LOW PRESSURE SENSOR)

1. Disconnect the pressure sensor connector.

2. Disconnect the A/C amplifier connector.

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

   Tester Connection (Symbols)	Condition	Specified Condition
   J58-18 (SG-3) - A56-1 (-S)	Always	Below 1 Ω
   J58-27 (S5-3) - A56-3 (+S)	Always	Below 1 Ω
   J58-32 (PSW) - A56-2 (CUT+)	Always	Below 1 Ω
   J58-18 (SG-3) - Body ground	Always	10 kΩ or higher
   J58-27 (S5-3) - Body ground	Always	10 kΩ or higher
   J58-32 (PSW) - Body ground	Always	10 kΩ or higher

NG	REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3. INSPECT LOW PRESSURE SENSOR

1. Install the manifold gauge set (Click here).

2. Connect the three 1.5 V dry cell batterie's positive (+) lead to terminal 3 and the negative (-) lead to terminal 1. Then connect the voltmeter's positive (+) lead to terminal 2 and the negative (-) lead to terminal 1. Measure the voltage.

   OK:

   The voltage changes according to refrigerant pressure, as shown in the graph.
   

NG	REPLACE LOW PRESSURE SENSOR

OK
PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE