Webasto Thermo 90, Workshop Manual

Thermo 90

8   Servicing

807

8.6.3.1 Installation Location

It is advantageous to mount the dosing pump in a cool 
location as near as possible to the tank. The ambient 
temperature must never 20° C for fuel and 
+40° C for Diesel operated installations at any time while 
in operation. The maximum pressure at the tapping 
location must be below 1.5 bar.

Dosing pump and fuel lines must not be installed in 
locations exposed to heat radiated by hot vehicle 
components. A heat shield is to be provided as required.

8.6.3.2 Installation and Attachment

The dosing pump is to be attached with anti-vibration 
mounts. The installation location is limited according to 
Fig. 807 to ensure sufficient self-venting capability. Due 
to the danger of corrosion the plug connection between 
dosing pump and dosing pump cable loom may only use 
Webasto original parts.

8.6.4 Fuel Filter

If there is the probability of contaminated fuel, only the 
Webasto filter, Order No. 487 171, may be used. The 
filter can be installed anywhere between the vertical and 
horizontal positions, but must be installed in the direction 
of flow.

8.6.5 Combustion Air Supply

Combustion air must under no circumstances be 
extracted from rooms with persons. The combustion air 
inlet must not point towards the forward direction of 
motion. It must be located so that no clogging by 
contamination, impact of snow, or intake of splash water 
is possible.

The combustion air intake line (inner diameter at least 
30 mm) may have a length from 0.5 m to 5 m with several 
bends of a total of 360°. Smallest bending radius is 
45 mm.

The combustion air inlet must not be located above the 
exhaust outlet.

NOTE

The combustion air intake line is to be routed in a 
downwards direction. If this is not possible, a water drain 
hole (4 mm Ø) must be provided at the lowest point.

If the heater is located near the fuel tank in a common 
installation compartment, combustion air must be taken 
in from, and the exhaust routed to, the exterior. The 

feed-throughs must be splash waterproof. 

If the heater is located in a closed installation box, 

a vent port of at least 6 cm

2

 is required. If the temperature 

in the installation box exceeds the permitted ambient 
temperature of the heater (see Technical Data), the vent 
port must be enlarged consulting Webasto.

8.6.6 Exhaust Line

The exhaust line (inner diameter 38 mm) may have a 
length from 0.5 m to 5 m and be routed with several bends 
(a total of 360°, smallest bending radius 85 mm). The 
exhaust muffler is mandatory and to be mounted near the 
heater.

In order to ensure the angle of 90° ± 10°, an attachment 
is required not further than 150 mm away measured from 
the exhaust pipe end.   

Fig. 808   Exhaust Muffler, Direction of Flow

The exhaust pipe outlet opening must not point in the 
direction of motion (see Fig. 808).

The exhaust pipe outlet opening must be located so as not 
to allow clogging by snow or mud.

Rigid exhaust-line pipes can be mode of unalloyed or 
alloyed steel, but must have a minimum wall thickness of 
1.0 mm. Flexible exhaust pipes must be made only of 
alloyed steel. The exhaust pipe is secured to the air heater 
with a clamp. For further requirements refer to official 
regulations.

For Thermo 90 TRS only: For official regulations 
concerning the exhaust pipe installation refer to Technical 
Information E3 - 5.10 (Order No. 776 623).

10

°

10

°

Exhaust exit direction

nearly vertical 90° ± 10°