Webasto Thermo 90: Diesel Heater Review & Info

hello everyone,

I inherited a Webasto Thermo 90 and installed it under the floor of my T4 van.

I would like to operate the heating system without a timer. Does anyone know if this is possible?
I only have a wiring diagram with a timer function from Websat.
I've installed a switch in between to control the circulation pump.
Does anyone happen to have a suitable circuit diagram?
I also have a question about the dosing pump: where should the voltage be applied?
and how is the pump timed? I'm not getting any diesel fuel to my engine!
'Gremlin wrote in another thread that the dosing pump should be installed in the supply line and not in the return line.'
Does a certain amount of pressure need to be present to start the pump?

best regards, renke

Hi!

What do you mean by "without the country code"?
Simply by manually flipping a switch?
It is technically possible, but you must not exceed the maximum operating time (without interruption). A timer automatically handles this, and you always have the option to start the heating process manually.
The dosing pump has 2 contacts between which the dosing cycle is applied as a 0-12V signal when the heating system starts. The pulse rate is estimated to be 1-2 Hz, depending on the operating mode.
Regarding the connection to the fuel system, there are some rules to keep in mind. Generally, the pumps are self-priming, but Webasto usually recommends installing a dedicated line with an appropriate fuel pickup. In one installation manual for a Thermo Top, I once read something about a maximum pressure above which the line should not be tapped into. With the return line, you're on the safe side; at worst, the heater won't work, but there is no risk of fuel being forced through the pump due to excessive pressure.
If the fuel pump is located outside the tank, a T-connector can also be used on its suction line to connect the suction line of the metering pump.

By the way, you can find installation instructions on www.techwebasto.com.

You can also find a contact form on www.webasto.de, where you can get in touch with their staff. They are very helpful and will send you instructions and tips via email.

I hope this helps for now...

Greetings,
Paul.