Mercedes 430S Class 2000 - Heater Problem

When you say "warm up" do you mean warm in the cabin or to just get the engine temperature up?

If you mean cabin tempearature, most Benz heating systems have an auxillary water pump in the heater line (usually low down on the passenger side of the engine compartment). If it stops so does most of the heat. On some systems and I think the S class is one of them, Benz also uses an electonically controlled water valve to control the amount of hot water going into the heater core. The default is full heat, but they do become corroded and I have seen a few stick partially open. After that most of the issues are in the very expensive electronic HVAC controls. From what I remember, most of the problems are from the auxillary pump or water vavle.

If you mean the enigne warming up, the most common failure is the thermostat.

The SRS light and seat heater are not related to the heater issue.

There is a 50/50 chance that the SRS light is on because of the cold or a sensor failure and not a failure of the entire system. It would be best to have this checked over though.

As for the seat heater, dig out the mutimeter and start testing components. I have seen fuses, switches, relays and even the grids themselves short out and stop working.

Thank you for your accurate and helpful advice.

Martin

Indeed it is the cabin temperature.