Heating system — general information (BMW 5 Series E34)

Fresh air enters the car through the air intake grille under the windshield. The air passes through the air distributor housing and is directed by a system of flaps controlled by cables to individual air nozzles. If the heating is set to the "heat" mode, cold air is directed to the heater radiator, where it is heated. The radiator is located in the heater housing and is heated by hot coolant. The flowing fresh air is heated by the hot lamellas of the heat exchanger and then enters the car. The heating has a water control mode, i.e. the temperature is regulated by the flow section of the radiator by two electromagnetic valves at the inlet of the heat exchanger.

The temperature in the cabin can be set by two switches on the left and right sides of the car. In accordance with the position of the switches and the current temperature, the electronic unit in the heater control panel regulates the opening time of the valves. The cabin temperature sensors are located behind the heater. Thanks to the presence of electronic regulation, a constant temperature in the cabin is maintained regardless of the speed of movement and the outside temperature.

To increase the heater's performance, a heater fan with four control stages is designed. To ensure different fan speeds, ballast resistors are switched on at different stages. If one of the resistors fails, the fan does not operate at the corresponding speed.

Note: Models equipped with air conditioning are not considered below. Except for maintenance (air conditioning compressor V-belt tension) all work related to the air conditioner must be performed at a service station.

(The original article is available on the website «BMWman»)