Webasto Thermo 90 ST Operating Instructions Manual

Dear Webasto Customer,

We presume that the principle and mode of operation of your new heater has been explained 

to your complete satisfaction by the workshop/service centre which installed the heater. In 

these operating instructions we would like to once again provide you with an overview of the 

safe use of the heaters. 

Within the territory governed by European Directive 70/156/EEC and/or EC/2007/46 (for new 

vehicle types from 29/04/2009), there are homologation approvals for the Thermo 90 S water 

heaters in accordance with the directives 2001/56/EC (Heating systems) and 72/245/EEC 

(EMC) and for the Thermo 90 ST water heaters in accordance with EC

E-R 122 (Heatings) and 

ECE

-R 10 (EMC). 

The units must be installed in accordance with the enclosed installation instructions. The in-

stallation must be checked in accordance with statutory installation provisions. Refer to the 

installation instructions for more details.

The year in which the heater was used for the first time must be permanently displayed on 

the type label by deleting the inapplicable years from the label. 

When installing the Thermo 90 S / Thermo 90 ST heater in vehicles for transporting dangerous 

goods, the requirements of the ADR in the respectively valid version must also be complied 

with in addition to the German Road Traffic Regulations (StVZO).

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. 

The heater must not: 

• be exposed to storage temperatures of more than +85 °C. 

Otherwise the electronics may suffer permanent damage. 

• Be operated without at least 20 % brand name anti-

freeze in the water of the heating circuit. 

General Information 

Maintenance and Safety Instructions 

Danger of explosion 

and suffocation!

Operating Instructions 

Thermo 90 S 

Thermo 90 ST