Heater function

Function

The heater enables a pleasant interior climate for the vehicle passengers in the event of different weather conditions.

A nominal temperature is preset at the heater pushbutton control module temperature selector switch. This setting is transmitted to the blend air flap in the heater housing via a cable and an actuation mechanism. Control is then carried out there as follows:

Temperature selector switch MIN setting (no heater output)

In this setting, the blend air flap blocks the route to the heat exchanger. The intaken fresh air is guided directly to the air outlets and therefore into the vehicle interior.

Temperature selector switch MAX setting (full heater output)

Due to the setting of the blend air flap, the intaken air is guided through the heat exchanger. Heated cooling water generally flows through this, as a result of which the passing air is heated. The temperature-controlled air is guided into the vehicle interior via the various air outlets.

Heating operation with PTC heater booster on engine 668.914

In these vehicles, an electrical PTC heater booster is additionally installed in the heater housing downstream of the heat exchanger in order to compensate the heater output deficit which occurs in the case of certain operating conditions.

The heater booster's five heating elements are supplied with current, and therefore become heated. As a result of the structural conditions, it is ensured that the fresh air intake flows directly through the electric PTC heater booster, and is therefore heated.