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