Webasto Thermo Pro 50 Eco Instruction manual

Water Heater
03/2003
Workshop Manual
Thermo Pro 50 Eco
Thermo Pro 50 Eco - D 24 V ADR
(Diesel, dangerous-goods transport)

Improper installation or repair of Webasto heating and cooling systems can cause fire or
the leakage of deadly carbon monoxide leading to serious injury or death.
To install and repair Webasto heating and cooling systems you need to have completed a
Webasto training course and have the appropriate technical documentation, special tools
and special equipment.
Only genuine Webasto parts may be used. See also Webasto air and water heaters
accessories catalogue.
NEVER try to install or repair Webasto heating or cooling systems if you have not completed
a Webasto training course, you do not have the necessary technical skills and you do not
have the technical documentation, tools and equipment available to ensure that you can
complete the installation and repair work properly.
ALWAYS carefully follow Webasto installation and repair instructions and heed all
WARNINGS.
Webasto rejects any liability for problems and damage caused by the system being installed
by untrained personnel.

Thermo Pro 50 Eco Table of Contents
I
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.1 Contents and purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.2 Meaning of signal words. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.3 Additional documentation to be used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.4 Safety precautions and regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.4.1 Statutory regulations governing installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.4.2 General safety precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
1.5 Spare parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
2 General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .201
2.1 Combustion-air fan unit with control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
2.2 Burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .202
2.2.1 Glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
2.3 Heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
2.3.1 Temperature sensor and overheating sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
2.3.2 Exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203
2.4 Circulation pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
2.5 Metering pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
2.6 Heater controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
3 Description of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301
3.1 Switch on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301
3.2 Starting and control mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
3.3 Switch off. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
3.4 Functions of heater in ADR vehicles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
4 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .401
5 Faults, Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .501
5.1 Troubleshooting without error code output. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .502
5.2 Troubleshooting with error code output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .507
6 Operating tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601
6.2 Operating checks in vehicle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .601
7 Circuit diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .701

Table of Contents Thermo Pro 50 Eco
II
8 Servicing work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 801
8.1 Work on heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 801
8.2 Work on vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 801
8.3 CO2 setting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 801
8.4 Circulation pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
8.5 DP42 metering pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
8.6 Checking work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
8.7 Heater, removal and installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
8.7.1 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
8.7.2 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
8.8 Restarting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 803
9 Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
9.1 Dismantling and assembling heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
9.1.1 Dismantling heater. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902
9.1.2 Assembling heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 902
9.2 Burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
9.2.1 Removing burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
9.2.2 Installing burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
9.3 Glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904
9.3.1 Electrical test of glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904
9.3.2 Removing glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
9.3.3 Installing glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
9.4 Combustion-air fan unit and control unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907
9.5 Heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908
9.6 Temperature sensor/Overheating sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
9.6.1 Checking sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
9.6.2 Removing temperature sensor/overheating sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
9.6.3 Installing temperature sensor/overheating sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
9.7 Exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
9.7.1 Checking exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
9.7.2 Removing exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
9.7.3 Installing exhaust temperature sensor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
9.8 Water connection piece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
9.8.1 Installing water connection piece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
10 Packing, Storage and Shipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001
10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001
10.2 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001
10.3 Transport. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1001

Thermo Pro 50 Eco Table of Illustrations
III
Table of Illustrations
Fig. 201 Thermo Pro 50 Eco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Fig. 202 Combustion-air fan unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
Fig. 203 Burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
Fig. 204 Heat exchanger. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Fig. 205 Exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Fig. 206 Example of U4847 Econ 24 V circulation pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Fig. 207 DP42 metering pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Fig. 208 Switch with operating indicator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Fig. 209 Standard timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
Fig. 301 Operating sequence Thermo Pro 50 Eco . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
Fig. 501 Overview of possible errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 502
Fig. 502 Overview of functional test of heater and its components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503
Fig. 503 Error code output by standard timer/switch with operating indicator . . . . . . . . . . . . . . . . . . . . . . . . . . . 507
Fig. 701 System wiring diagram for Thermo Pro 50 Eco with standard timer without ADR . . . . . . . . . . . . . . . . . . 703
Fig. 702 System wiring diagram for Thermo Pro 50 Eco with switch with operating indicator without ADR . . . . . 704
Fig. 703 System wiring diagram for Thermo Pro 50 Eco with switch with operating indicator with ADR . . . . . . . . 705
Fig. 801 Installation positions of U4847 Econ 24 V circulation pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
Fig. 802 Installation position of DP42 metering pump. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802
Fig. 901 Component description for Thermo Pro 50 Eco heater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 901
Fig. 902 Burner unit and combustion-air fan unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Fig. 903 Burner unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Fig. 904 Detailed illustration of cable routing for glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 903
Fig. 905 Burner unit with glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904
Fig. 906 Remove retaining spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Fig. 907 Remove cooling flag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Fig. 908 Remove glow plug . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Fig. 909 Installing glow plug. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Fig. 910 Installing cooling flag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 905
Fig. 911 Installing retaining spring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Fig. 912 Installing glow plug properly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Fig. 913 Installing glow plug. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Fig. 914 Routing glow plug cable with slight bend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906
Fig. 915 Glow plug cable, grommet and fuel pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 907
Fig. 916 Combustion-air fan unit with illustration of connectors
(variant shown is equipped with the maximum connector assignment) . . . . . . . . . . . . . . . . . . . . . . . . . . 907
Fig. 917 Heat exchanger. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908
Fig. 918 Moistening gaskets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909
Fig. 919 Position retaining spring while watching cable routing and position of sensors W5 and W6 . . . . . . . . . . 909
Fig. 920 Mounting screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910
Fig. 921 Tightening screw. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 910
Fig. 922 Removing exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
Fig. 923 Installing exhaust temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 911
Fig. 924 Retaining plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
Fig. 925 Retaining plate for installing water connection piece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 912
Fig. 1001 Preferred position of Thermo Pro 50 Eco heater for storage and transport . . . . . . . . . . . . . . . . . . . . . . 1001

1Introduction Thermo Pro 50 Eco
101
1 Introduction
1.1 Contents and purpose
This workshop manual serves to support instructed person-
nel, which repairs the Thermo Pro 50 Eco water heaters.
1.2 Meaning of signal words
Throughout this manual, the signal words WARNING,
IMPORTANT and NOTE have the following meanings:
WARNING
This heading is used to highlight operating instructions or
procedures which, if not or not correctly followed, may
result in personal injury or fatal accidents.
IMPORTANT
This heading is used to highlight operating instructions or
procedures which, if not or not correctly followed, may
result in damage to the equipment or its components.
NOTE
This heading is used to direct your attention to a special fea-
ture deemed essential to highlight.
1.3 Additional documentation to be used
Information of the general installation and operating
instructions is not contained in this workshop manual. If
repairs are necessary, these documents must also be used.
1.4 Safety precautions and regulations
In principle, the general accident prevention regulations and
current works safety instructions are applicable.
"General safety precautions" which go beyond the scope of
these regulations are listed in the following.
Any special safety regulations relevant to this instruction
manual will be highlighted in the relevant sections or text
passages of the procedures.
1.4.1 Statutory regulations governing
installation
Type approvals according to ECE-R 10 (EMC) and ECE-
R 122 (Heater) exist for the Thermo Pro 50 Eco heater.
For the installation, primarily the regulations of the directive
ECE-R 122 and the regulations contained in the installation
instructions must be observed.
NOTE
The regulations of these guidelines are binding in the scope
of the EU Directive 70/156/EEC and/or EC/2007/46 (for new
vehicle models from 29/04/2009) and should also be
observed in countries in which there are no special regula-
tions!
The Thermo Pro 50 Eco water heater was designed for use
in commercial vehicles.
The applicable regulations must be taken into account when
installing in special vehicles. Other uses are possible in con-
sultation with Webasto.
1.4.2 General safety precautions
The repair and commissioning of the unit may only be car-
ried out by professionals trained by Webasto. The repair and
installation of the unit may only be carried out in accordance
with the workshop manual and the installation instructions.
The year of initial start-up must be permanently
marked on the type label by removing the inapplica-
ble years.
The heaters are approved for heating the motor vehicle
engine and the vehicle cab, however not for heating the
hazardous-material cargo area.
The heater may only be installed in motor vehicles or in inde-
pendent heating systems with a minimum coolant quantity
of 4 litres.
The heater may not be installed in the cab or the passenger
compartment of vehicles.
When checking the coolant level, the procedure described
by the vehicle manufacturer must be followed.

Thermo Pro 50 Eco 1Introduction
102
WARNING
The heater must not be operated:
• In filling stations and tank farms.
• At locations at which highly flammable gases or dusts
can form, and at locations at which highly flammable
liquids or solid materials are stored (e.g. near fuel, coal
and wood dust, grain warehouses, dry grass and leaves,
cardboard, paper, etc.)
• In enclosed rooms (e.g. garages), not even via the timer
or Telestart.
• Without at least 20 % brand name anti-freeze in the
water of the heating circuit.
• outside the operating temperature range of -40 °C to
+80 °C. Otherwise the electronics may suffer
permanent damage.
There is a danger of burns, as the heater and the
attached parts may be extremely hot.
The heater:
• may only be operated with the fuel specified on the type
label and at the nominal voltage specified on the type
label.
• must be shut down by immediately switching off the
heater and removing the fuse in case of heavy smoke,
unusual combustion noises or fuel odours. The heater
must not be restarted until the unit has been checked
exclusively by professionals duly trained by Webasto.
• must be switched off during work in the engine
compartment and may not be cleaned with high-
pressure cleaning units or compressed air.
• Must be put into operation at least once a month for 10
minutes with the engine cold.
• should be checked by a professional every 2 years, at the
commencement of the heating period.
Liability:
• Non-compliance with the installation/operating
instructions and the warnings contained therein will
lead to the exclusion of all liability by Webasto. The
same applies if repairs are carried out incorrectly or with
the use of parts other than genuine spare parts. This will
result in the invalidation of the type approval for the
heater and therefore of its homologation/ECE type
licence.
Be sure to read the operating instructions of the heater
before commissioning.
1.5 Spare parts
The ID numbers of available spare parts can be found in the
Webasto spare parts catalogue or online at
http://dealers.webasto.com.

2 General description Thermo Pro 50 Eco
201
2 General description
Parking heating mode
The water heater is used in conjunction with the original
vehicle heating system in the parking heating mode for
– Cab pre-heating
– Engine pre-heating
– Pre-heating of other equipment (e.g. units).
The water heater operates independently of the vehicle
engine and is integrated in the vehicle's cooling system, fuel
system and electrical system.
Depending on the vehicle equipment, the ADR function (for
dangerous-goods transport vehicles) is provided.
Auxiliary heating mode
The water heater operates during engine operation and is
used to thermally support the cooling system. The water
heater is integrated in the cooling system, the fuel system
and the electrical system of the vehicle.
When the engine is shut off, the water heater is not auto-
matically switched off. An automatic switch-off function of
the water heater upon engine shut-off is only possible in
vehicle applications for transporting dangerous goods
(ADR).
NOTE
This workshop manual describes the retrofit variant of the
heater. For heaters installed directly at the vehicle manufac-
turer's plant, other control units with other connectors, soft-
ware or application parts may be used which are not
described in this manual. Information is only available for
these heaters via the documentation of the vehicle manu-
facturer.
The heater operates with regulation according to the cool-
ant temperature.
Depending on the deviation of the current coolant temper-
ature from the set-point temperature at the coolant temper-
ature sensor, the burner output is controlled within a range
of 2.5 to 5 kW.
The Thermo Pro 50 Eco heater consists of the combustion-
air fan unit (G) with the control unit, the heat exchanger (W)
and the burner unit (B).
The following components are arranged in the heater for
control and monitoring:
– Control unit
– Exhaust temperature sensor
– Coolant temperature sensor
– Overheating sensor
The fuel supply is provided from an external source via a
metering pump, which is connected to the fuel system of
the vehicle.
B = Burner unit assembly
G = Combustion-air fan unit assembly
W = Heat exchanger assembly
Fig. 201 Thermo Pro 50 Eco
G
W
B

Thermo Pro 50 Eco 2 General description
202
2.1 Combustion-air fan unit with control unit
The combustion-air fan unit contains:
• the heater type label
• the connection piece for the combustion air pipe
• the control unit with the plug-in contacts
• the engine and the impeller
The combustion-air fan unit supplies the air required for the
combustion process from the combustion air inlet to the
combustion chamber.
NOTE
It is not permissible to dismantle the combustion-air fan
unit.
2.2 Burner unit
The fuel-air mixture is processed and the actual combustion
takes place in the burner unit. The fuel flows via the fuel
pipe to the evaporator, where it is distributed and is evapo-
rated using the glow plug. The air required for combustion
is provided by the combustion-air fan unit and flows into the
combustion chamber via holes in the burner.
Fig. 202 Combustion-air fan unit
B1 = Combustion pipe with
evaporator mount and
evaporator
B2 = Retaining spring for
glow plug
B3 = Cooling flag for glow
plug
B4 = Glow plug
B5 = Fuel pipe
B6 = Glow plug cable
B7 = Grommet
B9 = Glow plug connector
Fig. 203 Burner unit
B1
B4
B2 B3
B5 B9
Pin 1
Pin 2
B6
B7

2 General description Thermo Pro 50 Eco
203
2.2.1 Glow plug
The glow plug (B4) is connected to the control unit via an
electrical line with a connector (B9). The glow plug is fas-
tened to the evaporator mount with a retaining spring (B2).
A cooling flag (B3) provides for heat dissipation from the
glow plug, and therefore reduces the temperature at the
glow-plug connection lines.
The fuel-air mixture is ignited with the glow plug when the
heater is started.
2.3 Heat exchanger
The heat generated in the heat exchanger by combustion is
transferred to the coolant circuit.
2.3.1 Temperature sensor and overheating
sensor
The temperature sensor detects the coolant temperature in
the heat exchanger of the heater as an electrical resistance.
This signal is fed to the control unit, where it is processed.
The temperature sensor (W5) and the overheating sensor
(W6) form a unit together with the cable and the connector.
The overheating sensor protects the heater against imper-
missibly high operating temperatures. This sensor triggers
the safety switch-off of the heater at a temperature higher
than125±8°C.
The temperature sensor is a semi-conductor component
with a negative temperature coefficient (NTC), i.e. the resist-
ance of the component decreases as the temperature
increases.
The overheating sensor is a semi-conductor component
with a positive temperature coefficient (PTC), i.e. the resist-
ance of the component increases as the temperature
increases.
In contrast to the temperature sensor, the characteristic
curve of the overheating sensor does not have a linear
behaviour. A sudden increase in the resistance occurs at
approx. 125 °C.
2.3.2 Exhaust temperature sensor
The exhaust temperature sensor (W7) is used to detect the
flame and impermissible exhaust temperatures.
Fig. 204 Heat exchanger
W1 = Heat exchanger
W2 = Cable of temperature sensors
W3 = Self-tapping screw, 40x10
W4 = Retaining spring for sensors
W5 = Temperature sensor
W6 = Overheating sensor
W7 = Exhaust temperature sensor, covered by retaining
spring (W9)
W8 = Self-tapping screw, 40x10
W9 = Retaining spring
W2 W5 W4 W3
W6
W1
W8W7, W9
Fig. 205 Exhaust temperature sensor

Thermo Pro 50 Eco 2 General description
204
2.4 Circulation pump
The U4847 24 Econ 24 V circulation pump ensures a feed
rate of the coolant in the vehicle heater and heater circuit.
The pump is switched on with the control unit and runs dur-
ing the entire operation of the heater. The circulation pump
is a centrifugal pump with a brushless EC motor.
The circulation pump is equipped with a 2-pin connector
socket which is connected to the control unit by means of a
separate wiring harness.
NOTE
Only the U4847 Econ 24 V circulation pump may be con-
nected to the Thermo Pro 50 Eco heater.
2.5 Metering pump
The fuel metering pump is a combined pumping, metering
and shut-off system. This dry-primeable reciprocating piston
pump supplies the fuel from the vehicle fuel tank to the fuel
connection piece of the heater via fuel lines. Installation is
usually carried out near the fuel tank. The metering pump is
not equipped with a pulsation damper. The metering pump
is connected to the heater with the heater wiring harness.
IMPORTANT
Only the model DP42 fuel metering pump may be used for
the Thermo Pro 50 Eco heater. Observe the model designa-
tion on the component for this purpose. When replacing the
metering pump, the CO2settings must be checked. see
Section 8.3.
2.6 Heater controls
The heater can be operated in two ways:
– Webasto BUS (W bus)
–Analogue
Examples of analogue control:
– Switch with operating indicator
– Standard timer
NOTE
Additional information on the respective heater control is
contained in the specific installation and operating instruc-
tions.
Fig. 206 Example of U4847 Econ 24 V circulation
pump
Fig. 207 DP42 metering pump
Fig. 208 Switch with operating indicator
Fig. 209 Standard timer

3 Description of Operation Thermo Pro 50 Eco
301
3 Description of Operation
3.1 Switch on
The heater is switched on depending on the equipment var-
iant with various heater controls (see Section 2.6).
Fig. 301 Operating sequence Thermo Pro 50 Eco
Glow plug
Meteringpump
Combustion-air
fan unit
Exhaust tem-
perature sensor
Operating indi-
cator lamp
Circulation pump
Vehicle fan
Possible encodable control temperatures
1) Switching on
2) Component check
3) Preheating 40 s.
4) Metering pump/partial load (1/4)
5) "Flame ON" detection
6) Stabilisation time
7) Full load
8) Vehicle fan "On"
9) Control range
10) Control break
11) "Flame OFF” detection
12) Run-on ended
13) Preheating 15 to 20 sec.
14) Metering pump/partial load (1/4)
15) "Flame ON" detection
16) Stabilisation time
17) Coolant temperature dropped
18) Full load
19) Switching off (run-on)
20) "Flame OFF” detection
21) Run-on ended

Thermo Pro 50 Eco 3 Description of Operation
302
3.2 Starting and control mode
After combustion begins (start), controlled heating auto-
matically begins.
At a higher coolant temperature, the heating capacity is
modulated between 2.5 kW and 5 kW. The objective to
achieve and maintain the control temperature.
The original vehicle heater fan does not switch until the
coolant is sufficiently heated (from approx. 30 °C).
If the coolant temperature increases above the set-point
value of the control temperature, the heater switches into
"OFF state ready". The circulation pump, the original vehicle
heater fan and the operation indicator continue to operate
during the "OFF state ready".
The heater starts again automatically after the coolant has
cooled to the pre-encoded restart temperature.
3.3 Switch off
When the heater is switched off, the operation indicator on
the heater control goes out. Combustion is ended and the
run-on begins. However, the circulation pump, the glow
plug and the combustion-air fan unit continue to run during
the run-on time to cool the heater. It is permissible to switch
on the heater again during the run-on. However, restarting
does not take place until after the run-on is complete.
IMPORTANT
A maximum run-on of 175 sec is activated when the heater
is switched off.
The heater supply voltage must be ensured for this time
(exception: ADR vehicles).
3.4 Functions of heater in ADR vehicles
The heater is put into operation with the heater control. An
ADR switch-off function will be triggered when
– the vehicle engine is shut down
(generator signal (D+) is eliminated),
– a pumping device is put into operation (auxiliary drive
signal (NA) is active).
In this case, combustion is ended and a reduced run-on, i.e.
the ADR run-on, is initiated. 40 seconds after the ADR case
occurs, the ADR run-on is ended.
Then the heater is in the "ADR lock-out" state. Before
restarting, the On/Off switch must be set to "Off" and the
auxiliary drive signal may no longer be active.
The isolating switch (Emergency-Stop switch) may only be
operated in case of danger, as the heater is switched off
without any run-on (overheating possible).

4 Technical data Thermo Pro 50 Eco
401
4 Technical data
The technical data is contained in the current version (part no. 9026479_) of the installation instructions.

Thermo Pro 50 Eco 5 Faults, Troubleshooting
501
5 Faults, Troubleshooting
General
This section describes troubleshooting on the Thermo Pro
50 Eco heater.
IMPORTANT
Troubleshooting work demands precise knowledge of the
structure and theory of operation of the various compo-
nents and must be carried out by trained personnel only.
The functional relationships are described in Section 2 and
3.
IMPORTANT
Error detection is generally limited to the localisation of the
defective components. The following fault causes are not
taken into account and should always be checked or a fault
should be excluded for the following reasons:
• Corrosion on connector
• Loose contact on connector
• Crimping error on connector
• Completeness of connector
• Corrosion on lines and fuses
• Corrosion on battery terminals
• Impermissible high ambient temperature
Each time an error is eliminated, a functional check must be
carried out in the vehicle; switch the heater off and on again
beforehand.
Procedure in case of errors or faults and lock-outs
IMPORTANT
Always determine the error cause for the lock-out first, then
eliminate the lock-out.
If errors occur in the heater, they will be detected by the
control unit as a fault. Depending on the type and weight-
ing of the fault, a fault run-on can be initiated. When a fault
run-on is initiated, the heater remains in fault lock-out. In
addition, an error code is output after a fault is detected
during the fault switch-off.
This is carried out by the operation indicator or by the switch
with an operating indicator. The error code is used by the
workshop or the authorised Webasto dealer for trouble-
shooting.
Fault causes
A fault occurs when one or more error have occurred. Pos-
sible errors are, e.g.
– Overvoltage/undervoltage
– Malfunctions of all components, e.g. due to a short cir-
cuit or open circuit
– Overheating of the heater
– Impermissible exhaust temperature
– False starts
– Flame failures
Elimination of fault lock-outs
1. Switch on heater
2. An error has occurred and is detected by the control
unit as a fault
3. The error code is output via the heater control
4. Any active heater lock-out is cancelled (as
described below)
4.1. The heater detects an error as a fault
4.2. Fault switch-off with subsequent fault lock-
out
4.3. The error code is output via the heater control
5. Switch off heater
6. Determine error cause (e.g. with or without error
code, visual inspection of fuses and connectors, etc.)
7. Eliminate error
8. Switch on heater
9. Fault lock-out unlocked
10. The heater switches into the control mode

5 Faults, Troubleshooting Thermo Pro 50 Eco
502
Certain errors result in the errors being added up in the error
memory. If the number of errors in the error memory has
exceeded a limit, the heater changes over to the heater lock-
out. The maximum number of errors in the error memory or
the error memory limit is defined by Webasto.
Cancel heater lock-out
The heater lock-out can be cancelled
– with the Webasto Thermo Test PC Diagnostics (WTT)
– or by switching on the heater.
Remove fuse F3 for at least 10 s.
Switch off heater.
Reinstall fuse F3.
Switch on heater.
5.1 Troubleshooting without error code output
Possible faults
The overview only shows some of the possible faults. The Webasto Service Hotline must be contacted in individual cases.
IMPORTANT
The error points specified from Tables Fig. 501 and Fig. 502 DO NOT match the error code numbers for error code output!
Heater Mode Fault Description Possible error point
(see Table Fig. 502)
Start Heater does not react, no component starts up, no display by opera-
tion indicator
6, 8
Heater smokes in start-up phase 1, 2, 4, 9, 11, 14, 15
Combustion
operation
Heater runs through start, however switches off prematurely 1, 3, 4, 5, 7, 9, 10, 11, 14,
15
Heater has rough combustion 1, 4, 9, 11, 14
Heater smokes in heating phase 1, 4, 9, 11, 14, 15, 16
Heater runs, vehicle interior cold 10, 12
Run-on Heater smokes in run-on phase 14
Other Fuel odour 1, 4, 9, 14
Exhaust odour in vehicle interior 11
Coolant loss 5, 10
Heater lock-out 13
Fig. 501 Overview of possible errors

Thermo Pro 50 Eco 5 Faults, Troubleshooting
503
Functional test of heater and its components
Error point Component Recommended workshop action Parameter
1 DP42 metering
pump
Check continuity from connector X11 (brown wire)
to earth.
Check continuity from connector X1, Pin 5 to con-
nector X11 (blue wire)
Measure coil resistance of DP42 metering pump, also
see Section 8.5
5.20 ohms ±5 % at
22±51°C,test
current: < 1 mA
Measure fuel feed rate (use Webasto Thermo Test PC
Diagnostics for controlling the metering pump), also
see Section 8.5
Diesel feed rate at metering
pump frequency of 7 Hz and
feed time of 60 s:
12.0 to 14.6 ml
Check connection of fuel line on all connection
pieces in accordance with general installation
instructions
2 Glow plug Measure glow plug resistance on glow plug connec-
tor X5 (green wire), also see Section 9.3.1
Cold resistance at 22 ± 5 °C:
0.780 ± 0.110 ohms
3 Sensors Check the cold resistance of the coolant temperature
sensor W5 on the connector X3 (Pin 2 and 4), also
see Section 9.7
Cold resistance at 22 ± 5 °C:
2,296 to 5,047 ohms, Test
current: < 1 mA
Check the cold resistance of the overheating sensor
W6 on the connector X3 (Pin 1 and 3), also see Sec-
tion 9.7
Cold resistance at 22 ± 5 °C:
30 to 250 ohms, Test
current: < 1 mA
Check the cold resistance of the exhaust tempera-
ture sensor W7 on the connector X6 (Pin 1 and 2),
also see Section 9.8
Cold resistance at 22 ± 5 °C:
2,050 to 2,220 ohms, Test
current: < 1 mA
4 Combustion-air
fan unit
Conduct component test on function of combus-
tion-air fan unit with Webasto Thermo Test PC Diag-
nostics. No rubbing noises may be heard.
Check CO2settings in accordance with Section 8.3
– Specify a set-point
speed of 6,000 rpm
– Listen for rubbing and
friction noises.
In addition, start-up
must be audible up to
the specified speed.
– No “Combustion air fan
blocking guard“ fault
message may occur.
5 U4847 Econ
24 V circulation
pump
Check wiring
Conduct component test to check function of circu-
lation pump with Webasto Thermo Test PC Diagnos-
tics
Touch pump with hand;
pump functions if slight
vibration or running can be
felt
Measure resistance on circulation pump connector
X4, also see Section 8.4
Resistance at 22 ± 5 °C:
20 ± 1 kohms
Check pump for leaks
Check self-venting installation position, also see
Section 8.4 or general installation instructions
Fig. 502 Overview of functional test of heater and its components

5 Faults, Troubleshooting Thermo Pro 50 Eco
504
6 Power supply Without Webasto Thermo Test PC Diagnostics
Measure power supply on heater connector X2,
Pin 1. Also see Fig. 701, Fig. 702 and Fig. 703.
Check fuse F2
Check power supply
With Webasto Thermo Test PC Diagnostics
Measure operating voltage from Webasto Thermo
Test PC Diagnostics
7 Undervoltage
detection
With Webasto Thermo Test PC Diagnostics
Measure operating voltage from Webasto Thermo
Test PC Diagnostics
– The voltage may not
drop below 20.0 V for
more than 10
consecutive seconds
– Check fuse F2
Without Webasto Thermo Test PC Diagnostics
Measure power supply on heater connector X2,
Pin 1. Also see Fig. 701, Fig. 702 and Fig. 703.
8 Operation indi-
cator
(standard timer
or switch with
operating indi-
cator)
When the immediate heat button/switch with an
operating indicator is operated, the light in the dis-
play/on the operating indicator is activated
Operation indicator of
standard timer:
– Measure power supply
on connector X9, Pin 11
– Check continuity on
connector X9, Pin 12 to
earth
– Check fuse F2
Operation indicator of
switch with operating indi-
cator
– Measure power supply
on switch with
operating indicator S4,
Pin A
– Check continuity on
switch with operating
indicator S4, Pin F to
earth
– Check fuse F2
9 Fuel
connection
Observe fuel fill level and fuel removal from tank
Check integration in vehicle fuel system
Check fuel lines for leaks, kinking and clogging,
especially in the area of the intake-side line connec-
tors
Disconnect the fuel line from the heater, hold the
hose in a catch container and operate the metering
pump with the Webasto Thermo Test PC Diagnostics
for 60 s at 7 Hz. When doing so, watch whether the
fuel is pumped bubble-free
If fuel sprays out of the line when the line is sepa-
rated from the heater, the fuel pipe of the burner
unit is probably clogged. If this is the case, the burner
unit must be replaced.
Error point Component Recommended workshop action Parameter
Fig. 502 Overview of functional test of heater and its components

Thermo Pro 50 Eco 5 Faults, Troubleshooting
505
10 Coolant circuit Check the integration in the vehicle coolant circuit in
accordance with the general installation instructions
IMPORTANT
Observe the direction of
flow of the coolant circuit.
Check the connection of the
coolant hoses to the water
connection piece according
to the marking (arrow mark-
ings) on the heater.
Check components for
leaks.
Eliminate kinks and rubbing spots
Check whether coolant circuit is correctly bled
Check for leaks on heater, water connection piece,
sensors, circulation pump and hoses and eliminate
Check circulation in coolant circuit
11 Exhaust system
and air intake
system
Check whether intake pipe and exhaust pipe are
routed in accordance with general installation
instructions
Check whether sufficient distance is present to pas-
senger compartment fresh-air intake of vehicle
No exhaust gas may be
sucked in through the com-
bustion air pipe
Check to make sure lines are not clogged
Eliminate existing leaks on intake pipe and exhaust
pipe (no CO2in intake air)
The exhaust pipe outlet may not be routed under the
intake pipe inlet
12 Vehicle fan Check fuse F1
Observe coolant temperature (K5 switches at
approx. 25 °C)
Check switching signal on the relay K5, ground on
Pin 85 and positive on Pin 86 (audible, also see wiring
diagram in general installation instructions)
Check coolant temperature signal wire (green/white,
gn/wh), Pin 86 on K5
13 Control unit/
heater locked
Determine error cause for lock-out, then eliminate
lock-out.
A distinction is made between 3 types of lock-out:
– Fault lock-out
Unlocking by pressing ON/OFF switch
–ADRlock-out
Unlock by operating the ON/OFF switch
When ADR is triggered by the auxiliary drive, it
must be deactivated before switching on the
heater again
– Heater lock-out
Unlock:
1) Switch on heater.
2) Remove fuse F3 for at least 10 s.
3) Switch off heater.
4) Reinstall fuse F3.
5) Switch on heater.
14 Burner unit Dismantling and visual inspection
Error point Component Recommended workshop action Parameter
Fig. 502 Overview of functional test of heater and its components