Welcome to Manins' truck camper project

Water/Air Heater

Webasto ThermoTop

The heater is a Webasto ThermoTop E water heater with heat exchanger and fan for air heating.

Rated at 12 V, 4.2 kW, S/N 1D1421070184. Model 10R-04 1232, 122R-00 0003.


There were some issues with the installation of the heater:

  • The Webasto activation switch, on the side of the base of the driver's side camper seat, was very easily knocked, inadvertently starting the heater.
  • The activation switch was illuminated all the time; a green LED next to the switch would come on when the switch was turned on; the heat exchanger fan had no indication for it being on.
  • It was not possible to turn on the heater and fan from the bed in the morning to warm the camper before we arose.
  • The heater runs to keep the water to a set temperature; this has very little relationship with the air temperature.

Recessed Webasto switch


Wiring behind the Webasto switch

I mounted the Webasto switch behind the switch panel, instead of in front of it, using four small nuts and bolts.

I rewired the Webasto switch so that its internal LED is on when the switch is on.

I changed the wiring to the green indicator LED so that it illuminates when the fan switch is on full or half speed. This required adding a couple of 1N4007 diodes.

I spliced in a length of 7-core trailer cable from the switches to the bed side of the kitchen bench and connected to a Carling-type double pole rocker switch that matches the others in the camper. The switch is wired in parallel with the Webasto switch and with the fan switch on full speed. Separate +12 V lines are used since the supply to the fan is separately fused. The wiring diagram is colour coded to show the different wires.


Wiring of the switches for the Webasto heater, fan and remote control.


Switch with guard.


Switch in wall at the Bed Head

The remote switch is set into a plastic guard to make inadvertent activation less easy. I made the guard from a section of 7-day pill box. The cutout is 38 mm x 21 mm and the guard walls are approx. 14 mm high.

Servicing the Heater

A good reference for servicing this kind of heater is by Le Tonkinois Varnish.