Webasto Thermo Top C-B Installation Instructions Manual page 40

Connection to the vehicle cooling system
7.1. Relocating the circulation pump
The circulation pump can be installed either in its intended position on
the heater or separately from the heater, in the water circulation. Care
must be taken to ensure without fail that water flows through the heater
in the right direction (water outlet at the top / water inlet at the bottom),
otherwise the heater will malfunction.
Fig. 5: Circulation pump U4847
Installation positions
38
Thermo Top C / Thermo Top E