Webasto Air Top Evo 3900 Operating Instructions Manual page 8

Error code Faultless operation:
The normal operation of the equipment is represented by the status
indicator, illuminating green light. After switching off the heater
(main switch) the status indicator shows the normal cooling down
process of the heater. After the heater has cooled down normally,
the status indicator shuts off.
Fault:
During an operational fault a flashing code is displayed by the
status indicator. This function enables a professional workshop to
solve the fault in a fast way. In this case please visit a Webasto
service station!