Installation manual

Webasto Product N.A., Inc. 8 www.techwebasto.com
Purpose / Version Thermo 90 S / Thermo 90 ST
3. Purpose / Version
3.1 Purpose of the Coolant Heater
The Webasto Thermo 90 S / Thermo 90 ST coolant
heaters are used in connection with the vehicle’s own
heating system
– to heat the cab,
– to defrost vehicle windows and
– to preheat water-cooled engines,
– to heat boats and motor-homes (recreational vehicles)
The water heater operates independently of the engine
and is connected to the cooling system, the fuel system
and the electrical system of the vehicle.
The Thermo 90 S and Thermo 90 ST heaters differ from
each other in their component connection arrangement
and in the fact that they have different control units.
3.2 Versions
3.2.1 Thermo 90 S version
Thermo 90 S gasoline
Water heater for "gasoline" fuel
Thermo 90 S diesel
Water heater for "diesel" fuel
The water heaters are designed for 12 V (Thermo 90 S
gasoline) and for 12 or 24 V (Thermo 90 S diesel).
3.2.2 Thermo 90 ST version
Thermo 90 ST gasoline
Water heater for "gasoline" fuel
Thermo 90 ST diesel
Water heater for "diesel" fuel
The water heaters are designed for 12 V (Thermo 90 ST
gasoline) and for 12 or 24 V (Thermo 90 ST diesel)