Webasto Thermo Top C in Boat Building & Maintenance Posted October 7, 2019 · Report reply Hi All, I'm having trouble getting my Webasto Thermo Top C to work. I have successfully tested the unit in the past so I know that it does actually produce hot water. But now I've installed it in the system it doesn't seem to want to run. I starts up and goes thru its start up checks, making a lot of noise, pulling in lots of air and then shuts off after 2-3 minutes. I did think it was the water not getting to the pump but I've swapped the pipes around a bit so I'm sure that there is water pressure enough get to the pump. Any ideas of what it could be? Or anyone know of a heating engineer in the Bristol area who might be able to help out? Many thanks, Laurence.