To repair a Webasto heater, first identify the problem; for example, if a Webasto Thermo Top heater does not turn on, it could be in fault lock-out mode. In this case, consult the service manual to deactivate this mode. If this does not solve the problem, check to see if power is getting to the heater, which requires more than 11.5 volts to operate. Ensure that the summer/winter switch is in the winter position, which is marked with a flame.
If the battery is dead, replace it or charge it to full capacity. Also, check and replace any broken fuses. A defective digital timer could cause the heater to malfunction. In this situation, bypass the timer by pressing the instant heat button, which is marked with a flame icon. If power is not reaching the timer, disconnect it and use a wiring diagram to troubleshoot the power supply.
If the heater still does not turn on, the cause could be a faulty transmitter. If the Telestart T70 transmitter is in the ventilating mode, consult the operator's manual, and reset it. Ensure proper allocation, and check that it has correctly installed fresh batteries. If the combustion air fan runs, but the heater fails to function, make sure that there is fuel in the intermediate reservoir. If the problem continues, check for disruptions in the fuel supply.
If the fuel is not reaching the heater, a faulty gasket could be the cause. However, in some cases the intermediate fuel reservoir may require replacement. If the heater starts, but only runs for a short time, ensure that it is mounted correctly and can draw in exhaust gas. Adjust the vehicle heating system to the warm setting, and turn on the fan to increase heat output.