2001 TOYOTA PRIUS air conditioning

BODY ELECTRICAL ± AIR CONDITIONING
165BE23
Discharge
Port
Variable
Scroll
DischargeSuction
Intake Port
Fixed Scroll
Compression161
Operation
1) Suction
As the capacity of the compression chamber, which is created between the variable scroll and the fixed
scroll, increases in accordance with the revolution of the variable scroll, refrigerant gas is drawn in from
the intake port.
2) Compression
From the state at which the suction process has been completed, as the revolution of the variable scroll
advances further, the capacity of the compression chamber decreases gradually. Consequently, the refrig-
erant gas that has been drawn in becomes compressed gradually and is sent to the center of the fixed scroll.
The compression of the refrigerant gas is completed when the variable scroll completes approximately
2 revolutions.
3) Discharge
When the compression of the refrigerant gas is completed and the refrigerant pressure becomes high, the
refrigerant gas discharges through the discharge port located in the center of the fixed scroll by pushing
the discharge valve.

BODY ELECTRICAL ± AIR CONDITIONING
165BE24
Condenser and Modulator
Scroll Compressor
with Oil Separator
Separator
Compressor Refrigerant Gas +
Compressor Oil
Compressor Oil
Evaporator Expansion
Valve 162
Oil Separator
1) General
A CS (Centrifugal with Shutter) type oil separator has been adopted to reduce the circulation rate of the
compressor oil that is intermixed with the refrigerant and circulates in the refrigeration cycle.
This oil separator is provided with a cylindrical pipe in the separator case, enabling the refrigerant gas
that has been discharged through the discharge gas inlet to be separated into refrigerant gas and oil
through centrifugal force, and minimizing the outflow of the oil to the discharge service port. As a result,
the oil circulation rate has been reduced and makes energy savings possible.

BODY ELECTRICAL ± AIR CONDITIONING
165BE26165BE25
Discharge Port
Discharge Service Port
Pipe
Oil Discharge Hole
Shutter
Oil Storage Chamber
Discharge ValveRefrigerant and
Compressor OilRefrigerant
Compressor
Oil
182BE20182BE19
Flow of Coolant
Bypass Valve
Water Pump OFF
(Engine ON)Bypass Valve
Water Pump ON
(Engine OFF)Flow of Coolant163
2) Construction and Operation
The refrigerant gas that is discharged from the discharge port flows by rotating around the cylindrical
pipe in the oil separator. At this time, the centrifugal force that is created during the rotation separates
the refrigerant gas and the compressor oil due to the difference in their specific gravity. The refrigerant
gas with the lighter specific gravity passes through the inside of the pipe and travels from the discharge
service port to the outside of the compressor. The compressor oil with the heavier specific gravity is dis-
charged through the oil discharge hole in the shutter and is stored in the oil storage chamber. Then, the
compressor oil is fed again into the compressor and circulates inside the compressor.
4. Water Pump (For Air Conditioning)
An electrical water pump with a bypass valve that provides a stable heater performance even if the engine
is stopped due to a function of the THS has been adopted.
When the engine is running, this water pump ceases its operation and opens the bypass valve to minimize
the flow resistance of the coolant that is pumped by the engine water pump.

BODY ELECTRICAL ± AIR CONDITIONING
182BE21
One Touch Clip
Glove Compartment Door
Stopper PinClean Air Filter
Service Tip
The replacement interval for the clean air filter is 30,000 km or 2 years.
However, it varies with the use conditions (or environment). 164
5. Clean Air Filter
A clean air filter that excels in removing pollen and dust is standard equipment.
This filter, which cleans the air in the cabin, is made of polyester. Thus, it can be disposed of easily as a com-
bustible material, a feature that is provided in consideration of the environment.
To facilitate the replacement of the filter, a one-touch clip is used in the filter cover which is unified with filter
case. Thus, a construction that excels in serviceability has been realized.

BODY ELECTRICAL ± AIR CONDITIONING
182BE22
Air
Conditioning
ECUBEAN
ECM
Room Temper-
ature SensorEvaporator Tem-
perature SensorSolar SensorAmbient Tem-
perature SensorEngien Coolant
Temperature Sensor
182BE23
Ambient Temperature Sensor165
6. Air Conditioning ECU
General
An automatic control type air conditioning has been adopted. This system uses an air conditioning ECU
to perform the calculation of the required outlet air temperature control, temperature control, blower con-
trol, air inlet control, air outlet control, and compressor control.
The information that is necessary for effecting the controls are the signals from the room temperature
sensor, evaporator temperature sensor, and solar sensor that are directly transmitted to the air condition-
ing ECU, and the signals from the ambient temperature sensor and the engine coolant temperature sensor
that are transmitted via the ECM. These signals are calculated by the air conditioning ECU to effect the
proper control.

System Diagram 
Sensors
1) Ambient Temperature Sensor
The ambient temperature sensor has been pro-
vided on the left, in front of the condenser.
The signals from this sensor are transmitted to
the air conditioning ECU via the ECM.

BODY ELECTRICAL ± AIR CONDITIONING
182BE24Room Temperature
Sensor
182BE25
Evaporator Temperature
Sensor
182BE26
Solar Sensor
182BE27
Engine Coolant
Temperature Sensor 166
2) Room Temperature Sensor
The room temperature sensor has been pro-
vided inside the instrument finish lower panel.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
3) Evaporator Temperature Sensor
The evaporator temperature sensor has been
provided behind the evaporator in the air
conditioning unit.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
4) Solar Sensor
The solar sensor has been provided on top of
the instrument panel.
The signals from this sensor are directly trans-
mitted to the air conditioning ECU.
5) Engine Coolant Temperature Sensor
The water temperature sensor has been pro-
vided on the water outlet area on the left side
of the engine.
The signals from this sensor are transmitted to
the air conditioning ECU via the ECM.

BODY ELECTRICAL ± AIR CONDITIONING
182BE50
Large
Target
Damper
Opening
Angle
Small
Large Small
Tentative Damper Opening Angle167
Calculation of Required Outlet Air Temperature (TAO: Temperature Air Outlet)
After receiving the signals from the sensors and the temperature control switch setting, the air conditioning
ECU uses the formula shown below to calculate the required outlet air temperature, to regulate the servomo-
tors and blower motor. This is an outlet air temperature that is required in maintaining the set temperature
in a stable manner.
TAO=KSETx TSET±Kr x TR±KAMx TAMdisp±KsxTS+C±TCTA O = KSET x TSET ± Kr x TR ± KAM x TAMdisp ± Ks x TS + C ± TC
KSET= Setting Temperature Coefficient TSET = Setting Temperature
Kr = Room Air Temperature Coefficient TR = Room Air TemperatureKr= Room Air Temperature CoefficientTR= Room Air Temperature
K
AM= Ambient Air Temperature Coefficient TAMdisp = Ambient Air TemperatureAMppp
Ks = Solar Radiation Coefficient TS = Solar Radiation
C = Correct Constant TC = Compressor ON / OFF CorrectC= Correct ConstantTC= Compressor ON / OFF Correct
= Constant
Temperature Control System
1) Air Mix Damper Control
In response to the temperature control switch setting, the required ambient temperature, evaporator tem-
perature sensor, and engine coolant temperature sensor compensations are used by the air mix damper
control to calculate a tentative damper opening angle, through an arithmetic circuit in the air mix damper,
to arrive at a target damper opening angle.

Calculating the Target Damper Opening 

BODY ELECTRICAL ± AIR CONDITIONING
174BE06
Ex-HI
Blower
Air
Volume
LO
Low
Required Outlet
Air TemperatureHigh[C]
174BE07
HI
Calculated
Air Volume
LO
OFF[C]
Coolant Temperature (a) (b) (c) 168
Blower Control System
1) Blower Motor Startup Control
When the blower motor is started up, the blower voltage in the auto mode (low speed) is output to the
blower controller for 3 seconds. This is designed to protect the blower controller from a sudden startup
current surge.
2) Manual Control
Sets the blower speed according to operation of the blower switch.
3) Automatic Control
a. Stepless Air Volume Control
As shown on the right, when the AUTO
switch on the heater control panel is pushed,
the air conditioning ECU automatically reg-
ulates the voltage to the blower controller, in
accordance with the required outlet air tem-
perature, to deliver stepless air volume.
b. Warm-Up Control
When the coolant temperature detected by the engine coolant temperature sensor is below a predeter-
mined level and the air outlet is in the FOOT or BI-LEVEL mode, the blower does not operate. When
the coolant temperature reaches specified temperature (b), the blower motor operates at low speed.
When the coolant temperature is between specified temperature (b) to (c), the air flow calculation using
the engine coolant temperature sensor signal, and, the air flow calculation using the required outlet air
temperature are compared, and the lesser of the two is automatically selected as the air flow to be used.
When the coolant temperature reaches specified temperature (c) or more, the blower motor runs at high
speed. Moreover, when the coolant temperature is under specified temperature (a), and the warm-up
control is effected (blower motor off), the air outlet is switched to the DEF mode. Later, when the blower
motor turns on, the air outlet changes from the DEF mode to the FOOT or BI-LEVEL mode.