The heating and ventilation system is designed to maintain the optimum temperature in the cabin when the ambient temperature changes
Two electric motors force air into the cab through the heater core.
The radiator is connected to the engine cooling system through a shut-off valve, which is activated by a lever from the cab.
When the tap is turned on, the engine radiator blows warm air into the cab, and the system operates in heater mode.
When the radiator is off, the motors blow cold air into the cab and the system operates in ventilation mode.
The circuit diagram of the heating and ventilation system (Fig. 1) includes two ME250 electric motors, a relay of electric motors of type 11.3747.010, a key switch of type A147-01.11, which controls the operating modes of electric motors. The latter operate in two modes depending on the position of the key switch, which connects them in series or in parallel.
The voltage to the electric motors is supplied by the relay of the electric motors through the fuse for a current of 10 A, and the voltage to the winding of the relay of the electric motors is supplied from the terminal "K3" of the instrument switch and the starter through the fuse for the current of 7.5 A.
Therefore, the electric motors can only be turned on with the key switch after turning the instrument switch and starter to position "1"
The order of the system is as follows:
- - When the battery (ground) switch is turned on, the voltage from the batteries is supplied through the ammeter to the terminal “AM” of the instrument and starter switch and then to terminal 30 of the heater motor relay;
- - when the instrument and starter switch is set to position II, voltage is applied from terminal K3 through a fuse for a current of 7.5 A to the motor relay winding (pin 85), the relay operates and supplies voltage from pin 30 to pin 87 and then through a 10 A fuse on terminals 80B and 80E of the electric motor (upper in the diagram) and terminal 80E of the heater motor switch;
- - when the switch of electric motors is turned to position "1", its outputs 80V - 80G and 80D are closed, and the electric motors are connected in series relative to the voltage of the on-board network and operate at a low speed, since each engine will have half the voltage of the on-board network. li>
Current path for powering electric motors:
“+“ of the battery —► starter motor —► output B of the starter relay —► ammeter, output “AM” of the instrument and starter switch —► closed terminals 30 and 87 of the electric motor relay —► fuse for a current of 10 A —► terminal 80B electric motor (upper) -► output 80V of the electric motor and switch of electric motors -► outputs 80G -► 80D switch -► output 80D of the electric motor (lower) housing -► switch "mass" - "-" battery;
- - when the switch is turned to position “2”, its outputs 80D and 80E, 80V and 80G are connected to each other, which leads to parallel connection of motors. In this case, they are switched on to the full voltage of the on-board network and operate at a higher speed.
You can also regulate the temperature of the incoming warm air using the heater radiator valve.
In winter conditions, when the fans are running, it is not recommended to close the tap completely to prevent water freezing in the radiator.
The design, operation and replacement of the heater are discussed in the article - The heating and ventilation system of the KAMAZ vehicle