SSP 880153

Service Training
Self Study Program 880153
The Heat Pump from Volkswagen
Design and Function
Volkswagen Group of America, Inc.
Volkswagen Academy
Printed in U.S.A.
Printed 7/2015
Course Number SSP 880153
©2015 Volkswagen Group of America, LLC.
All rights reserved. All information contained in this manual is based
on the latest information available at the time of printing and is
subject to the copyright and other intellectual property rights of
Volkswagen Group of America, LLC., its affiliated companies and
its licensors. All rights are reserved to make changes at any time
without notice. No part of this document may be reproduced, stored
in a retrieval system, or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording or otherwise, nor
may these materials be modified or reposted to other sites without
the prior expressed written permission of the publisher.
All requests for permission to copy and redistribute information should
be referred to Volkswagen Group of America, Inc.
Always check Technical Bulletins and the latest electronic repair
information for information that may supersede any information
included in this booklet.
Trademarks: All brand names and product names used in this manual
are trade names, service marks, trademarks, or registered trademarks;
and are the property of their respective owners.
Contents
Introduction .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 1
Basic Principle of the Heat Pump. .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 5
The Heat Pump in the e-Golf.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 7
Components.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 10
Function of the Heat Pump.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 20
System Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Service .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 27
Knowledge Assessment.  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  .  . 28
Note
This Self-Study Program provides information
regarding the design and function of new
models.
Important!
This Self-Study Program is not a Repair Manual.
This information will not be updated.
For maintenance and repair procedures, always
refer to the latest electronic service information.
i
Page intentionally left blank for printing purposes
Introduction
Heat pump technology has been used in buildings for many years to reduce heating and cooling costs. At Volkswagen, this
efficient technology is being used to produce heat in the e-Golf.
The heat pump system is a refrigerant circuit that is made up of numerous components. In this SSP, we will simply call it the
heat pump.
In cars with an internal combustion engine, the heat produced by the engine can be used to heat the passenger compartment.
Electrically driven vehicles, however, do not produce enough thermal energy to heat the vehicle interior.
Using a heat pump allows the heat from the outside air and the heat produced by the drive components to heat the vehicle
interior. As a result, less battery power is required by the electrical high-voltage heater, reducing energy consumption. The
range of the e-Golf with a heat pump is 30% greater with a heat pump than without one.
s532_006
1
Introduction
Physical Laws
What is heat?
Heat (mathematical symbol of Q, unit of joule) is a form
of energy that is transferred between two systems due to
temperature differences.
Heat always flows from a body of high temperature to a
body of low temperature.
Heat can be transferred through thermal conduction,
thermal radiation or convection.
Phase Transition
s532_002
The phases of water
There are three primary states of matter that substances
can change between due to temperature or pressure; solid,
liquid and gas.
Freezing
Condensation
Melting
Vaporization
To change its state of matter, a body must either absorb or
release thermal energy:
• Melting: The transition from solid to liquid state. Heat
is absorbed.
• Vaporization: The transition from a liquid to a gaseous
state. Heat is absorbed.
• Condensation: The transition from a gaseous to a
liquid state. Heat is released.
• Freezing: The transition from a liquid to a solid state.
Heat is released.
2
Solid
Liquid
Gas
Introduction
Heat Pump
General Information
Heat pump technology makes use of these laws.
Water flows downhill by itself, but needs to be pumped uphill. The same can be said of heat: it automatically “flows” from a
higher to a lower temperature level. Heat pumps use electrical energy to pump heat against the natural “temperature flow”
from a lower to a higher temperature level.
Task
Heat pumps transport thermal energy from one location to another. They have been used in buildings for a long time for
heating. Heat pumps have lower energy consumption, lower pollution levels and lower operating costs than traditional heating
methods.
Source of Heat
Heat Pump
Heating
s532_004
When reversed, this principle is used for cooling in refrigerators and air conditioning systems.
3
Introduction
Refrigerant
The heat pump uses R134a refrigerant. It is a chlorofluorocarbon (CFC) with a low boiling point. R134a is invisible in gas form
and is colorless like water when in vapor and liquid states.
Characteristics
F
• Designation: 		
tetrafluorethane
• Chemical formula:
CH2F-CF3
• Boiling point: 		
-26.5°C (at approx. 1 bar)
• Solidification point:
-101.6°C
• Critical temperature:
100.6°C
• Critical pressure:
4.056 MPa (40.56 bar)
F
F
C
C
H
F
s532_042
H
Pressure and Boiling Point
The boiling point is the temperature at which a substance changes from liquid to gaseous state. The boiling point of a
substance is always given at normal atmospheric pressure (1.01325 bar). The boiling temperature varies according to the
pressure. It falls at low pressure and rises at high pressure. This behavior is illustrated as an evaporation curve in the pressuretemperature graphs.
Water
R134a
bar
1.0
9
0.9
8
0.8
7
Pressure [bar]
Pressure [bar]
0.7
0.6
0.5
0.4
0.3
6
5
4
3
2
0.2
1
0.1
s532_054
s532_052
0 10 20 30 40 50 60 70 80 90 100
-40
-20
0
20
40
60
These physical properties of R134a refrigerant are used in the heat pump. By specifically changing the pressure and the
temperature, the refrigerant is able to:
–– evaporate and absorb heat at ambient temperature or
–– condense and release heat at ambient temperature.
4
Basic Principle of the Heat Pump
Circuit Design
A heat pump basically consists of the following main components: a compressor, an evaporator, an expansion valve and a
condenser.
In the closed heat pump circuit, the refrigerant circulates and changes between liquid and gaseous state, transferring and
transporting heat. There is always a high pressure side and a low pressure side in this circuit.
Outside Air
(airflow/fan)
Expansion Valve
Evaporator
Cooled Air
Outside Air
(airflow/fan)
Electrical Power
Supply
Compressor
Heated Air for Interior
s532_033
Condenser
Function
• The compressor draws in cold, gaseous refrigerant at low pressure and compresses it under high pressure. The
temperature rises. In this phase, the refrigerant is gaseous and under high pressure at a high temperature.
• Cold air (airflow/fan) flows through the condenser. The refrigerant transfers heat to the air and condenses. The heated
air flows into the interior. In this phase, the refrigerant is liquid and under high pressure at medium temperature.
• The pressure of the liquid refrigerant is reduced significantly in the expansion valve. The reduced pressure leads to
partial evaporation of the refrigerant. After expansion, the temperature of the refrigerant is significantly lower than the
ambient temperature.
• In the evaporator, the pressure of the refrigerant being sprayed is further reduced and it evaporates. The heat of
vaporization required for this process is drawn from the warmer outside air, which then cools. The now gaseous
refrigerant leaves the evaporator.
5
Basic Principle of the Heat Pump
Phase Diagram of R134a Refrigerant
Pressure [bar]
This diagram represents the phases of R134a in a heat pump circuit. You can see the energy content, the pressure, the
temperature and the state of the refrigerant in each process. Other absolute values occur depending on the outside air
temperature and the heating requirement inside the vehicle.
s532_012
Energy Content (kJ/kg)
Gaseous Refrigerant
High-pressure Region
Wet Steam Region of Refrigerant
Low-pressure Region
Liquid Refrigerant
Line of Constant Temperature (temperature curve)
Gas/liquid Region Borderline
Explanation
A - B: compression
The refrigerant is gaseous; the pressure and the
temperature rise.
B - C: condensation
The refrigerant turns to liquid, the temperature falls
and the pressure remains constant.
C - D: expansion
The pressure reduction leads to partial evaporation of
the refrigerant and the temperature falls.
6
D - A: evaporation
The refrigerant becomes completely gaseous, the
temperature rises slightly and the pressure remains
constant.
K: critical point
The boiling line is to the left of the critical point and
the saturated vapor line is to the right of it.
The Heat Pump in the e-Golf
System Configuration
Components like the electrical air conditioner compressor, the evaporator and the condenser run the air conditioning system
in the e-Golf. The refrigerant circuit of the air conditioning system has been expanded for use with the heat pump to include
refrigerant lines, electrical expansion valves, pressure senders, temperature senders and a heat condenser.
Since the heat pump system for the e-Golf also uses the heat produced by the motor and the power and control electronics for
electric drive, a second expansion valve and a heat exchanger for the heat condenser are used in parallel to heat pump circuit.
Refrigerant Circuit
Pressure and Temperature Sensors
Expansion/Shut-off Valves
Condenser
Electrical Air Conditioner
Compressor
Heat Exchanger for Heat Condenser
Evaporator
s532_007
Heat Condenser
7
The Heat Pump in the e-Golf
Schematic Diagram of the Coolant and Refrigerant Circuits
This schematic diagram provides a basic illustration for subsequent descriptions of components and the functions of the heat
pump.
G395
V470
G829
N642
Refrigerant Circuit
Reservoir
N643
N696
G827
G826
N636
Condenser
N637
G828
Heat Condenser
N638
Evaporator
Heat Exchanger for Heat Condenser
G110
G787
Z115
Non-return Valve
G785
Coolant Circuit
AX4
V509
N632
G931
VX54
G789
JX1
G788
V508
G83
N687
8
s532_090
Radiator
The Heat Pump in the e-Golf
Key
AX4 		High Voltage Battery Charger 1
G83 		Engine Coolant Temperature Sensor on Radiator Outlet
G110 		A/C Engine Coolant Temperature Sensor
G395 A/C Pressure/Temperature Sensor
G785 		Temperature Sensor in Front of High Voltage Heater (PTC)
G787 		Temperature Sensor after Heat Exchanger
G788 		Temperature Sensor after Electro-Drive Drive Motor
G789 		Temperature Sensor after Electric Drive Power and Control Electronics
G826 		A/C Pressure/Temperature Sensor 2
G827 		A/C Pressure/Temperature Sensor 3
G828 		A/C Pressure/Temperature Sensor 4
G829 		A/C Pressure/Temperature Sensor 5
G931 		Temperature Sensor Before Charger
JX1 		Electric Drive Power and Control Electronics
N632 		Coolant Change-Over Valve 1
N636 		Refrigerant Expansion Valve 1
N637 		Refrigerant Expansion Valve 2
N638 		Refrigerant Expansion Valve 3
N642 		Refrigerant Cut-off Valve 4
N643 		Refrigerant Cut-off Valve 5
N687 		Radiator Bypass Switch-over Valve
N696 		Refrigerant Cut-off Valve 1
V470 		Electrical A/C Compressor
V508 		Coolant Pump In Front of Electric Drive and Power Control Electronics
V509 		Coolant Pump In Front if High Voltage Heater (PTC)
VX54 		Three-phase Current Drive
Z115 		High Voltage Heater (PTC)
		Refrigerant Circuit
		Coolant Circuit
The following terms are shortened in the remainder of this SSP:
• N636 Refrigerant Expansion Valve 1 to Expansion Valve 1 (EV1)
• N637 Refrigerant Expansion Valve 2 to Expansion Valve 2 (EV2)
• N638 Refrigerant Expansion Valve 3 to Expansion Valve 3 (EV3)
• N696 Refrigerant Cut-off Valve 1 to Cut-off Valve 1 (SV1)
• N642 Refrigerant Cut-off Valve 4 to Cut-off Valve 4 (SV4)
• N643 Refrigerant Cut-off Valve 5 to Cut-off Valve 5 (SV5)
9
Components
Electrical Air Conditioner Compressor
Location
Electrical A/C Compressor
The Electrical A/C Compressor V470 is bolted to the Threephase Current Drive VX54.
Design
The e-Golf with heat pump uses an electrical air conditioner
compressor with an internal scroll compressor design. It
is identical to the air conditioner compressor used in the
e-Golf without a heat pump.
s532_024
Function
The electrical A/C compressor draws in the gaseous
refrigerant at low pressure. It is compressed, the pressure
increases and the temperature of the refrigerant rises.
The electrical A/C compressor pushes the refrigerant to
the condenser as a hot gas. This compressor forms the
separating point between the low and high-pressure sides of
the refrigerant circuit.
s532_021
10
Components
Heat Condenser and Evaporator
Location of Heat Condenser/
Evaporator
The heat pump in the e-Golf has a heat condenser and
an evaporator. Both are located in the heater and air
conditioning unit.
Design of Heat Condenser
Evaporator
Heat Condenser
s532_026
The heat condenser is a serpentine-like pipe system with
fins. This creates a large heat exchange area with good
heat transfer. Airflow from the fan passes through the heat
condenser.
Heat Condenser
Heat Condenser Function
Condensation is the transition of matter from a gaseous to
a liquid state.
s532_009
The hot, gaseous refrigerant reaches the condenser. The
condenser pipes and fins absorb heat as cool outside air
flows across the condenser. As it cools, it condenses and
becomes a liquid. The cooled refrigerant is then guided
into the vehicle interior.
11
Components
Evaporator Design
The evaporator has a similar design to the heat condenser
and also has an internal flow of refrigerant. Air from
the heater and air conditioning unit flows through the
evaporator.
Evaporator
Evaporator Function
s532_025
The evaporator works as a condenser during heat pump
operation (“heating” function). This means that the air
flowing through the evaporator is heated.
The evaporator works as an evaporator in
“cooling” mode (function). This means that
the air flowing through the evaporator is
cooled.
Expansion Valves and Cut-off Valves
Locations of Expansion Valves/
Cut-off Valves
Three expansion valves and three cut-off valves are used in
the heat pump circuit:
N643
N642
N696
N636
• N636 Refrigerant Expansion Valve 1 (EV1)
• N637 Refrigerant Expansion Valve 2 (EV2)
• N638 Refrigerant Expansion Valve 3 (EV1)
• N696 Refrigerant Cut-off Valve 1 (AV1)
• N642 Refrigerant Cut-off Valve 4 (AV4)
• N643 Refrigerant Cut-off Valve 5 (AV5)
12
N637
N638
s532_028
Components
Design of Expansion Valves
Expansion Valve
The expansion valves have an identical design. A V-shaped
control edge in the ball valve enables on-demand, stepless
activation (0-100 percent).
s532_011
Expansion Valve Function
Refrigerant flows through the Expansion Valve
2 N637 from the evaporator in the direction
of the condenser in “heating” operating
mode (function). In “cooling” operating mode
(function), the refrigerant flows through the
expansion valve in the opposite direction.
The refrigerant can expand in the expansion valve, i.e. fill
a considerably larger space (volume enlargement). The
pressure then falls significantly. The liquid refrigerant
partially evaporates, causing the temperature to fall.
Design of cut-off valves
Cut-off Valve
The cut-off valves are ball valves that are either fully open or
fully closed.
Cut-off Valve Function
s532_017
The cut-off valves regulate the flow direction of refrigerant in
the refrigerant circuit.
The expansion valves and cut-off valves are connected to the Thermal Management Control Module J1024 via
the same LIN-Bus. Each compact valve connector has its own coded pin assignment.
13
Components
Condenser
Location
The condenser is located between the radiator fan and the
radiator.
Design
The condenser is a conventional air conditioner condenser.
Condenser
s532_030
Function
The condenser operates either as an evaporator or
a condenser according to the “cooling” or “heating”
operating mode (function).
It works as an evaporator in heat pump mode, i.e. in the
“heating” function. Evaporation refers to the transition from
a liquid to a gaseous state.
In the evaporator, the refrigerant, which is no longer under
pressure and is at ambient temperature, is completely
evaporated. The heat required for this is drawn from
the outside air that passes between the evaporator fins.
The pressure of the refrigerant remains constant and the
temperature rises slightly.
The evaporator functions as a condenser in
“cooling” operating mode (function).
14
s532_019
Components
Heat Exchanger for Heat Condenser
Location
The heat exchanger is located on a bracket mounted on
the bulkhead in the engine compartment. Most of the heat
pump components are mounted on it.
Design
The Heat Exchanger for Heat Condenser is just like
conventional oil-to-coolant plate heat exchangers.
Heat Exchanger for
Heat Condenser
s532_046
The coolant circuit is separate from the refrigerant circuit.
Heat is exchanged without direct contact between or mixing
of the fluids.
Key
Refrigerant circuit
Coolant circuit
Function
Connections for
Refrigerant
In the Heat Exchanger for Heat Condenser, the heat of the
coolant is transferred to the refrigerant and the refrigerant
evaporates.
Connections for
Coolant
The heat from electronic components such as the threephase current drive, the power and control electronics for
electric drive and the charging unit is used.
s532_013
15
Components
Reservoir
Reservoir
Location
The reservoir is upstream of the electrical air conditioner
compressor in the refrigerant flow direction.
The reservoir is located at the front right in the wheel
housing.
Design
It is identical to the reservoir in other vehicles with air
conditioning.
s532_034
Refrigerant Outlet
to Electrical Air
Conditioner
Compressor
Refrigerant
Inlet
Function
The reservoir is used in the refrigerant circuit as an
expansion and supply tank for the refrigerant. Since the
thermal loading of the evaporator and condenser and
the speed of the electrical air conditioner compressor will
vary during operation, different quantities of refrigerant
will also be pumped through the circuit. The reservoir
is incorporated into the circuit to compensate these
fluctuations.
s532_023
16
Components
Refrigerant Pressure and Temperature Sensors
Location
G395
A total of five refrigerant pressure and temperature sensors
are installed in the heat pump circuit.
G829
They are located on the assembly carrier:
G827
• G395 A/C Pressure/Temperature Sensor
G826
• G826 A/C Pressure/Temperature Sensor 2
• G827 A/C Pressure/Temperature Sensor 3
• G828 A/C Pressure/Temperature Sensor 4
G828
• G829 A/C Pressure/Temperature Sensor 5
s532_044
Function
The refrigerant pressure and temperature sensors measure
the pressure and the temperature of the refrigerant, convert
the readings into an electrical signal and send it to the heat
pump control module.
The following data is collected:
• Refrigerant pressure 0 to 36 bar
• Refrigerant temperature -40°C to +150°C
• Internal temperature sender -40°C to +140°C
s532_015
Failure Effects
The refrigerant pressure and temperature
sensors can only be replaced after the
refrigerant has been extracted.
If one or more sensors fail, the refrigerant pressure and the
refrigerant temperature are determined using a map. The
heating up phase for the vehicle interior is increased and an
entry is made in the event memory.
17
Components
Coolant Change-Over Valve 1 N632
Location
The Coolant Change-Over Valve 1 is located in the coolant
circuit.
Design
The Coolant Change-Over Valve 1 is a 3/2-way valve.
Z115
AX4
N632
JX1
Function
This valve is used to switch between the large coolant circuit
and the small coolant circuit with the high voltage heater
(PTC). When not powered, it is constantly open and only
the large coolant circuit is active. The heat-up phase of the
vehicle interior takes longer.
s532_092
To High-voltage
Heater (PTC) Z115
s532_027
From the Power and
Control Electronics for
Electric Drive JX1
18
To the Charging Unit 1 for
High-voltage Battery AX4
Components
Thermal Management Control Module J1024
Location
This control module is located in the engine compartment
under the 12 V battery.
It is connected to the Data-Bus On-Board Diagnostic
Interface J533 via the Extended CAN-Bus.
Function
s532_051
The Thermal Management Control Module J1024 takes
care of all functions that are associated with controlling the
refrigerant circuit.
Failure Effects
If the Thermal Management Control Module J1094 fails, the
entire air conditioning system will not operate.
19
Functions of the Heat Pump
Heating Function in Air Mode
Electrical Air Conditioner Compressor
SV4
SV5
SV1
EV1
Heat Condenser
Evaporator
Condenser
EV2
EV3
Key
s532_014
EV
Expansion valve
SV
Shut-off valve
High-pressure area
Mid-pressure area
Low-pressure area
This function uses only the heat from the outside air to heat the vehicle interior.
1. The electrical air conditioner compressor compresses the refrigerant. The gaseous refrigerant is under high pressure at a
high temperature.
2. In the heat condenser, the refrigerant transfers heat to the air and starts to condense. The heated air flows as heating air
into the vehicle interior.
3. Cut-off valves 1 and 4 are closed. The pressure is reduced via Expansion Valve 1. The temperature of the liquid refrigerant
decreases.
4. The evaporator now works as a condenser. The incoming refrigerant condenses and releases heat. The now pre-heated air
flows to the heat condenser.
5. Expansion Valve 3 is closed. The refrigerant pressure is lowered further via Expansion Valve 2. The refrigerant temperature
now falls below the ambient temperature.
6. The cold refrigerant, which is below ambient temperature, evaporates in the condenser. The heat of vaporization required
for this process is drawn from the warmer outside air, which then cools down. The gaseous refrigerant leaves the condenser
and flows through the open Cut-off Valve 5 in the direction of the air conditioner compressor.
20
Functions of the Heat Pump
Phase Diagram of the R134a Refrigerant
Pressure [bar]
This diagram shows the state of the R134a refrigerant during the heating function (air mode).
Energy Content (kJ/kg)
Explanation
A - B: compression (electrical air conditioner compressor)
The refrigerant is gaseous; the pressure and the temperature
rise.
D - E: condensation (evaporator) 				
The refrigerant condenses, the temperature falls and the
pressure remains constant.
B - C: condensation (heat condenser)			
The refrigerant turns into liquid, the temperature falls and
the pressure remains constant.
E - F: expansion (Expansion Valve 2) 		
The pressure is relieved via Expansion Valve 2. The
temperature falls below the ambient temperature.
C - D: expansion (Expansion Valve 1)			
The pressure is relieved via Expansion Valve 1. This leads to
partial evaporation of the refrigerant and the temperature
falls.
F - A: evaporation (condenser)			
The refrigerant becomes completely gaseous, the
temperature and the pressure remain constant.
K: critical point 					
The boiling line of the refrigerant is to the left of the
critical point and the saturated vapor line is to the right of
it.
21
Functions of the Heat Pump
Heating Function in Coolant Mode
Refrigerant Circuit with Large Coolant Circuit
Electrical Air Conditioner Compressor
SV4
SV5
Section of Small Coolant Circuit
EV1
SV1
Heat Exchanger for
Heat Condenser
Z115
Evaporator
EV2
Condenser
EV3
V509
s532_050
Heat Condenser
Z115
Key
V509
EV 		Expansion Valve
AX4
SV 		Cut-off valve
AX4 		High Voltage Battery Charger 1
N632
JX1 		Electric Drive Power and Control Electronics
VX54
N632 		Coolant Change-Over Valve 1
JX1
N687 		Radiator Bypass Switch-Over Valve
V508 		Coolant Pump in Front of Electric Drive and
Power Control Electronics
V508
V509 		Coolant Pump In Front of High Voltage Heater
(PTC)
N687
s532_048
VX54 		Three-phase Current Drive
Z115 		High Voltage Heater (PTC)
		High-pressure Area
		Mid-pressure Area
		Low-pressure Area
		Coolant
		Refrigerant Circuit
22
		Coolant Circuit
Functions of the Heat Pump
Refrigerant Circuit
This function uses the thermal energy from the coolant circuit (three-phase current drive, power and control electronics and
battery charging module).
1. - 4. The compressor compression and condensation in the evaporator is identical to the heating function in air mode.
5. Expansion Valve 2 is closed. The pressure is relieved by Expansion Valve 3 and the temperature of the liquid refrigerant 		
decreases.
6. The refrigerant evaporates in the Heat Exchanger for Heat Condenser due to the addition of heat. The heat of vaporization 		
required for this process is drawn from the warmer coolant, which then cools down. The gaseous refrigerant leaves the heat 		
exchanger for heat condenser and flows in the direction of the air conditioner compressor.
Large Coolant Circuit
The coolant flows through the large coolant circuit to pull heat from the heat from the three-phase current drive, the power
and control electronics and the battery charging unit. This circuit is run by the Coolant Pump in Front of Electric Drive Power
and Control Electronics V508. The radiator is bypassed by actuating the Radiator Bypass Switchover Valve N687 to use heat
efficiently.
Small Coolant Circuit
If the evaporation output of the large coolant circuit and the air is not sufficient, additional energy is supplied to the coolant
circuit and the coolant is heated by activating the High Voltage Heater (PTC). To prevent the three-phase current drive, the
power and control electronics for electric drive and the battery charging unit from heating up, the large coolant circuit is isolated
from the small coolant circuit by actuating the Coolant Change-Over Valve 1 N632. The small coolant circuit is operated by
activating the Coolant Pump in Front of the High Voltage Heater (PTC).
23
Functions of the Heat Pump
Heating Function in Combined Air and Coolant Mode
Electrical Air Conditioner Compressor
SV4
SV5
SV1
EV1
Heat Condenser
Evaporator
Condenser
s532_020
Heat Exchanger for
Heat Condenser
EV2
EV3
Key
EV 		Expansion valve
SV 		Cut-off valve
		High-pressure area
		Mid-pressure area
		Low-pressure area
This function is a combination of the two functions described above. Heat from the outside air and the heat from the coolant
are used simultaneously to heat the vehicle interior.
1. - 4. The process from compression in the electrical air conditioner compressor to complete condensation in the evaporator is 		
		 identical to the heating function in air mode.
5. 		 Expansion Valves 2 and 3 reduce the pressure. As a result, the temperature of the liquid refrigerant drops. After 			
		 expansion, the refrigerant temperature is lower than the ambient temperature. The heat pump control module regulates 		
		 how much refrigerant flows through each of the two expansion valves.
6. 		 The cold refrigerant, which is below ambient temperature, evaporates in the condenser. The heat of vaporization 		
		 required for this process is drawn from the warmer outside air, which then cools. The gaseous refrigerant leaves the 		
		 evaporator and flows through the open Cut-off Valve 5 in the direction of the air conditioner compressor.
7. 		 The refrigerant evaporates in the Heat Exchanger for Heat Condenser due to the addition of heat. The heat of
		 vaporization required for this process is drawn from the warmer coolant. The gaseous refrigerant leaves the Heat
		 Exchanger for Heat Condenser and flows in the direction of the air conditioner compressor.
24
Functions of the Heat Pump
Cooling Function
Electrical Air Conditioner Compressor
SV4
Heating Flap
SV5
SV1
EV1
Heat Condenser
Evaporator
Condenser
s532_022
EV2
EV3
Key
EV 		Expansion valve
SV 		Cut-off valve
		High-pressure area
		Low-pressure area
In this function, the heat pump circuit uses cold temperatures to cool the vehicle interior.
1. The electrical air conditioner compressor compresses the refrigerant. The gaseous refrigerant is under high pressure at a
high temperature.
2. Cool air does not flow through the heat condenser since the heating flap is closed. The refrigerant does not condense here
and also does not release any heat.
3. Expansion Valve 1 closes the access to the evaporator. The refrigerant flows through the open Cut-off Valve 1 to the
condenser.
4. The airflow passes through the condenser. The refrigerant transfers heat to the air and condenses. The temperature of the
refrigerant falls, the pressure remains constant.
5. The pressure and the temperature of the liquid refrigerant are reduced via Expansion Valve 2. After expansion, the
refrigerant temperature is lower than the ambient temperature.
6. The refrigerant evaporates completely in the evaporator. The heat of vaporization required for this process is drawn from the
outside air, which then cools down. The cooled air flows into the vehicle interior.
7. The gaseous refrigerant leaves the evaporator and flows through the open Cut-off Valve 4 in the direction of the air
conditioner compressor.
25
System Overview
Sensors
Actuators
Diagnostic Connection
Climatronic Control Module J255
Data-Bus On-Board Diagnostic Interface J533
Convenience CANBus
Refrigerant Expansion
Valve 1 N636
A/C Engine Coolant
Temperature Sensor G110
Refrigerant Expansion
Valve 2 N637
A/C Pressure/Temperature
Sensor G395
A/C Pressure/Temperature
Sensor 3 G827
CAN-Bus Extended
A/C Pressure/Temperature
Sensor 2 G826
Refrigerant Expansion
Valve 3 N638
Refrigerant Cut-off
Valve 1 N696
Refrigerant Cut-off
Valve 4 N642
A/C Pressure/Temperature
Sensor 4 G828
A/C Pressure/Temperature
Sensor 5 G829
Refrigerant Cut-off
Valve 5 N643
Thermal Management Control Module J1024
LIN-Bus
Coolant Change-Over
Valve 1 N632
Electrical A/C
Compressor
V470
s532_038
High Voltage Heater (PTC)
Z115
26
Service
The heat pump system is maintenance-free. The repair manual must be followed when emptying and filling the system. There
are no special tools.
Only persons qualified to work on air conditioning systems may perform work on the heat pump system.
Before beginning servicing work on the heat pump system, please observe the repair manual information about any procedures
that require de-energization by a High-Voltage Technician (HVT).
27
Important Links
https://www.datarunners.net/vw_crc/default.asp?pageid=home
www.vwwebsource.com
www.vwhub.com
Knowledge Assessment
An on-line Knowledge Assessment (exam) is available for this Self-Study Program.
The Knowledge Assessment may or may not be required for Certification.
You can find this Knowledge Assessment at:
www.vwwebsource.com
For Assistance, please call:
Volkswagen Academy
Certification Program Headquarters
1-877-791-4838
(8:00 a.m. to 8:00 p.m. EST)
Or, E-mail:
[email protected]
29
Volkswagen Group of America
2200 Ferdinand Porsche Drive
Herndon, VA 20171
July 2015