2001 TOYOTA PRIUS Service Repair Manual

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