Acura CSX. Manual — part 475

Symptom

Diagnostic procedure

Also check for

21-18

Climate Control

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Warm air comes out of
the vents, and there is
frost on the expansion
valve

Probable cause: The expansion valve is stuck
closed
Replace the expansion valve (see page 21-80)

HVAC DTCs (see page 21-9)
Check the old expansion valve
for contamination. If
contaminants are found,
replace the A/C system
component that caused the
contamination

The temperature of the
liquid line is the same
on both sides of the
expansion valve, and
the evaporator coil or
suction line has heavy
condensation

Probable cause: The expansion valve is stuck
open
Replace the expansion valve (see page 21-80)

HVAC DTCs (see page 21-9)
Check the old expansion valve
for contamination. If
contaminants are found,
replace the A/C system
component that caused the
contamination

Warm air comes out of
the vents, but
operation is normal
otherwise

Probable cause: Compressor failure
Do the A/C system test (see page 21-99), and
correct any problems. If necessary, replace the
compressor (see page 21-83)

HVAC DTCs (see page 21-9)
Add refrigerant oil depending
on the part you replaced
(see page 21-7)

Driver’s and
passenger’s side vent
temperatures vary by
more than 11 °C (20 °F)

Probable causes: The recirculation control door
or the air mix door is malfunctioning
Do the following troubleshooting:

Recirculation control motor test (see page
21-74)
Air mix control motor test (see page 21-72)

HVAC DTCs (see page 21-9)
Poor or loose connections at the
terminals

Insufficient heating

1.
2.
3.

4.

5.

6.
7.

Check the coolant level (see page 10-7)
Check the radiator cap (see page 10-4)
Check the coolant temperature during normal
operation
Check the heater core inlet hose temperature:

If it is COLD, check for restrictions in the hose,
a damaged or leaking thermostat, or a
damaged or leaking water pump
If it is HOT, check for restrictions in the
heater core. Back flush or replace the heater
core

Do the air mix control motor test (see page
21-72)
Check the blower motor unit for obstructions
Check for air leaks around the ducts and vents

HVAC DTCs (see page 21-9)
Damaged cylinder head gasket

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21-19

System Description

EXPANSION VALVE
(Meters the required amount of
refrigerant into the evaporator)

RECEIVER/DRYER
DESICCANT
(Traps debris, and
removes moisture)

A/C COMPRESSOR
(Suction and compression)

A/C CONDENSER
(Radiation of heat)

A/C PRESSURE SENSOR
(Triple function)

BLOWER FAN

EVAPORATOR
(Absorption of heat)

EVAPORATOR TEMPERATURE SENSOR

RELIEF VALVE
(Relieves pressure at the A/C compressor
when the pressure is too high)

HIGH PRESSURE VAPOR

HIGH PRESSURE LIQUID

LOW PRESSURE LIQUID

LOW PRESSURE VAPOR

The air conditioning (A/C) system removes heat from the passenger compartment by transferring heat from the
ambient air to the evaporator. The A/C system refrigerant expands in the evaporator, and the evaporator becomes
very cold and absorbs the heat from the ambient air. The blower fan pushes air across the evaporator where the heat
is absorbed, and then it blows the cool air into the passenger compartment.

This vehicle uses HFC-134a (R-134a) refrigerant, which does not contain chlorofluorocarbons. Pay attention to the
following service items:

• Do not mix refrigerants CFC-12 (R-12) and HFC-134a (R-134a). They are not compatible.
• Use only the recommended polyalkyleneglycol (PAG) refrigerant oil (SP-10) designed for the R-134a A/C

compressor. Intermixing the recommended (PAG) refrigerant oil with any other refrigerant oil will result in A/C
compressor failure.

• All A/C system parts (A/C compressor, discharge line, suction line, evaporator, A/C condenser, receiver/dryer,

expansion valve, O-rings for joints) are designed for refrigerant R-134a. Do not exchange with R-12 parts.

• Use a halogen gas leak detector designed for refrigerant R-134a.
• R-12 and R-134a refrigerant servicing equipment are not interchangeable. Use only a recovery/recycling/charging

station that is U.L.-listed and is certified to meet the requirements of SAE J2210 to service the R-134a air
conditioning systems.

• Always recover refrigerant R-134a with an approved recovery/recycling/charging station before disconnecting any

A/C fitting.

When the refrigerant is below
196 kPa (2.0 kgf/cm , 28 psi)
or above 3,138 kPa (32 kgf/cm ,
455 psi), the ECM/PCM turns the
compressor relay off to protect
the A/C compressor.
When the refrigerant is above
1,470 kPa (15.0 kgf/cm , 213 psi),
the A/C pressure sensor
switches the radiator and
A/C condenser fans to high speed.

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Oil Separator

21-20

Climate Control

OUTLET SIDE
(To A/C condenser)

OIL SEPARATOR

FROM INSIDE
A/C COMPRESSOR

INLET SIDE
(To inside
A/C compressor)

EVAPORATOR

A/C COMPRESSOR

A/C CONDENSER

EXPANSION VALVE

HIGH REFRIGERANT OIL FLOW

LOW REFRIGERANT OIL FLOW

OIL SEPARATOR

Oil emission from the A/C compressor to the A/C line is reduced by placing the oil separator in the A/C compressor.
This results in a thinner oil film inside of the heat exchangers (A/C condenser and evaporator). Air conditioning
efficiency is increased without sacrificing engine performance.

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A/C Pressure Sensor

A/C System Pressure

Sensor Output

Voltage (V out)

System Operation

21-21

99

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1)

14

0

196
(2)

28

3,138
(32)

455

kPa
(kgf/cm )

psi

V

4.575

0.684

0.425

0.2945

OUTPUT
VOLTAGE
(Vout)

Vcc 5 V

Vout

GND

A/C PRESSURE

2

The A/C pressure sensor converts A/C pressure into electrical signals to the ECM/PCM.

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Abnormally low pressure: Below 196 kPa
(2.0 kgf/cm , 28 psi)

Below 0.685 V

The ECM/PCM disengages the compressor
clutch. The radiator and condenser fans
operate based on engine coolant temperature.

Normal operating pressure:

Above 196 kPa (2.0 kgf/cm , 28 psi)
Below 1,470 kPa (15.0 kgf/cm , 213 psi)

0.686 V to 1.944 V

The ECM/PCM cycles the compressor clutch
based on cooling demand. The radiator and
condenser fans operate at low speed unless
the engine coolant temperature exceeds 206 °F.

High operating pressure:

Above 1,470 kPa (15.0 kgf/cm , 213 psi)
Below 3,138 kPa (32 kgf/cm , 455 psi)

1.945 V to 4.575 V

The ECM/PCM cycles the compressor clutch
based on cooling demand. The radiator and
condenser fans operate at high speed.

Abnormally high pressure: More than
3,138 kPa (32 kgf/cm , 455 psi)

Above 4.575 V

The ECM/PCM disengages the compressor
clutch. The radiator and condenser fans
operate based on engine coolant temperature.

: The A/C system pressure can be monitored in the HDS PGM-FI Data List.

The response of the A/C pressure sensor is shown in the graph.

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