Webasto Thermo Pro 90 HDD Operating Instructions Manual page 5

If a fault code is displayed, please contact your authorised Webasto dealer. The work-
shop can use the fault code to narrow down the problem.
The workshop also has the option of carrying out detailed troubleshooting using computer
diagnostics.
The heaters may only be repaired by trained personnel.
– In the case of control elements with display, the malfunction is
shown on the display in the form of a fault code made up of a
combination of digits and letters.
– In the case of control elements with lights, the malfunction is
shown in the form of a flash code. After 5 fast flash pulses, the
fault code is output by a sequence of long flash pulses. The long
flash pulses must be counted. This number (fault code) provides
information to the workshop about the type of malfunction on
the heater.