The heating system is designed for continuous operation for a long time and provides multiple air exchange in the cabin, the required air speed and temperature, the temperature of the cabin surfaces
The cabin is heated by air heated in the heater radiator 19.
Outside air passes through the grille between the windshield and hood, changes direction and is separated from rainwater.
Then, the air from the air intake duct 10 enters the heater casing and, depending on the location of the mixing dampers, enters either through the heater radiator or directly into the left 5 and right 9 air flow distributors.
The heating and ventilation unit (HVU) consists of a heater body 11. It includes a casing 4 and a cover 1 of the casing, connected through a gasket 6 by brackets 7, left 5 and right air flow distributors 9, fastened to the casing and the cover of the heater casing with screws 8, radiator 19, radiator cover 21, electric fan 16, fan cover 12, outside air mixing dampers, air distribution dampers and ventilation dampers located inside the ROV body and controlled by rails 8 and 9 of the protective cover 10, which prevents damage to the rails during installation.
An additional resistor 8 is installed on the cover of the OVU casing, which provides three speeds of rotation of the electric fan.
The heater is mounted on the bracket through rubber bushings 11 with two bolts 9 to the wall of the engine compartment and bolt 3 through the rubber bushing to the cross member 19 of the OVU mounting bracket.
The heater valve is driven by a microelectric motor through a mechanical gearbox; the valve has two positions - fully open or fully closed.
The OVU radiator is connected by hose 23 to the heater control valve and to the engine cooling system by hoses 15 and 17.
The hoses are connected to the hoses of the engine compartment through a clip 14 attached to the wall of the compartment with two nuts 16.
A tee 12 is installed in the heater hose system to eliminate air locks in the piping system of the water heater when filling (replacing) the engine cooling system with coolant.
The air distribution unit is connected to the air distribution channels made in the instrument panel through air ducts 6 and 7
Fig. 3 Controls
Fig. Heating and ventilation control panel
The outdoor air conditioner is controlled by regulators 1 2, 3 and 4, located on the heating and ventilation control panel.
1 — air flow distribution regulator knob in the cab: 
- air flows to the windshield and side windows;
—air enters the chest area of the driver and passenger;
- air enters the windshield and side windows, chest and legs of the driver and passenger; 
—air only enters the legs of the driver and passenger;
2 — knob for adjusting the amount of air entering the cabin. Has four positions:
—off;
—minimum fan performance;
— average fan performance;
—maximum fan performance;
3—plug (for GAZ-2705) or knob for adjusting the intensity of air heating in the GAZ-2705 "Combi" cab or in the passenger compartment of buses 4 - knob for adjusting the air temperature in the cab (the knob simultaneously controls the heater tap and mixing dampers).
The leftmost position of the handle (wide The second part of the blue symbol) corresponds to the ventilation mode.
In this position of the handle, the heater valve is closed, and the mixing dampers, controlled by rod 18, completely block the channel for the supply of outside air to the heater radiator and the ventilation channel is completely open.
The intermediate and extreme right positions of knob 4 (the wide part of the red symbol) correspond to the heating mode.
In this mode, when the knob is turned 9° clockwise, the tap is open, the mixing dampers partially open the channel for outside air to the heater radiator and partially block the ventilation channel (intermediate switching on of the heating system).
In the extreme right (clockwise) position of the handle, the ventilation channel is completely blocked and the entire flow of outside air goes through the heater core.
To heat the cab open the heater valve, turn knob 4 clockwise by an angle of at least 9° and then turn knob 4 choose a comfortable air temperature.
Removing frost and condensation
To quickly remove frost and condensation from the windshield and side windows, you must:
- - set air distribution control 1 to position
- - set the air temperature controller 4 to the extreme right position (the wide part of the red symbol);
- - air volume controller 2 set to maximum fan performance.
To get a comfortable climate - you need:
- - set the air distribution regulator 1 to the position you have chosen;
- - temperature controller 4 to set the desired air temperature (outside air temperature or heat air from the heater);
- - turn the air quantity regulator 2 from position 0 to one of the three positions to obtain the desired air flow rate into the passenger compartment.
The central and side ventilation grilles on the instrument panel have handles (levers) for controlling dampers, by moving which you can change the direction of air flow, increase or decrease the amount of incoming air until the air intake duct is completely closed.
To quickly remove fogging and frosting on the windows, set the knob 1 to direct the air flow to the windshield and side windows, the knob 4 to the extreme right position (the wide part of the red symbol), and the knob 2 to the extreme right (clockwise) position maximum rotation speed of the electric fan of the outdoor unit.
Fig. 5 Air flow distribution in the vehicle cabin.
The distribution of air flows in the cabin is carried out through air ducts and nozzles 1 2, 3, 4, 5 and 6.
Side 2 and 5 and central pipes 3 and 4 for blowing the driver and passenger have damper control levers.
By moving them, you can change the direction of air flows, increase or decrease the amount of incoming air, up to the complete closure of the channel of its intake.
The efficiency of the heating system depends on the temperature of the coolant in the engine, which must be maintained within 85-100 ° C during the cold season.
Ventilation system is designed to create a normal microclimate in the cab during vehicle operation in the summer.
The cab is provided with supply and exhaust ventilation systems.
Forced supply ventilation is carried out through the outdoor ventilation unit with the windows closed, the sunroof (if any) and the heater tap closed
To turn on ventilation, turn knob 4 to the extreme left position (the wide part of the blue symbol) and turn knob 2 to set the required air supply rate to the cabin.
The rightmost position of knob 2 corresponds to the maximum rotation speed of the electric fan.
Select, by turning knob 1, the distribution of air flows in the cabin.
Using the control levers for the dampers of the nozzles, set the most comfortable air direction.
Forced ventilation should be used in hot weather at low vehicle speeds and in parking lots.
At vehicle speeds above 50 km/h, forced ventilation can be carried out with the electric fan switched off due to high-speed air overpressure. Supply ventilation is also carried out through the sliding glass doors.
Exhaust ventilation is carried out through the slots associated with the atmosphere and located at the bottom of the cabin doors.
Checking the technical condition and maintenance of the heating and ventilation unit (HVU)
Technical information maintenance of the air conditioner is reduced to periodic checks of the technical condition of the heater radiator, tap and system hoses, the operation of the electric fan, the air heater dampers and nozzles on the instrument panel that distribute and direct the air flows supplied to the cab.
When engine coolant leaks into the cab, you must first check the reliability of fastening the heating system hoses with clamps, the tightness of the radiator and heater valve.
If a leak is detected at the joints, it is necessary to tighten the clamps 13.
If the cause of the leak is the heater radiator (liquid is leaking from the OHU housing), the radiator must be removed, the place of fluid leakage should be identified and the leak eliminated.
Heater radiator 19 prefabricated, tubular-lamellar with plastic tanks.
The core of the radiator is made of aluminum tubes and aluminum cooling plates.
A metal bottom with a rubber gasket is installed on both sides of the core.
The gasket seals the ends of the tubes, and the tank installed on this gasket is pressed against the gasket by folding antennae.
Helical plastic turbulators are installed inside the tubes for greater heat removal from the heater radiator.
If a leak is found at the place where the pipes are sealed with a rubber gasket, eliminate it by pressing the folding antennae on the bottom of the tank.
To do this, you need to securely install the radiator on a rubber mat and slightly press the mustache of the metal bottom at the place of leakage.
If fluid leaks through damaged tubes, the radiator should be replaced with a new one.
In case of repair, it is necessary to remove the tanks by bending the antennae of the bottom of the tank, and put repair tubes of a smaller diameter with their subsequent burnishing (that is, with an increase in the inner diameter of the tubes).
If valve 22 is leaking, it must be removed and inspected.
If a leak is found at the connection of the cover to the body, tighten the screws securing the cover or unscrew the screws and replace the gasket.
To check the operation of the faucet, put your finger on the faucet body and turn handle 4 by 9-10° from the extreme left position clockwise.
In this case, power is supplied to the electric drive of the crane and a click of the shut-off damper should be heard.
If there is no click, the drive is defective.
The faucet needs to be replaced. The electric fan of the outdoor unit does not work - or it works with increased noise.
The reason for stopping the electric fan 16 may be a power failure of the fan, jamming of the fan rotor in the heater housing, seizure of the motor shaft in the bearings, or unreliable contact in the electrical wire connector 14.
To eliminate jamming of the fan rotor, it is necessary to remove the electric fan, make sure that the two brackets for fixing the electric fan flange 17 are in place and do not jam the electric fan rotor.</p >
It is necessary to turn the rotor and make sure that the motor shaft rotates freely.
If rotation is difficult or the rotor does not rotate at all, replace the electric fan.
If turning knob 2 to turn on the fan does not change the airflow rate, check the connection of resistance 8 (terminal) to the wiring harness or replace the resistance.
Disassembly and repair of the heating and ventilation system
To remove the heater core:
- - drain the coolant from the engine cooling system (3—4 l);
- - loosen the hose clamps 15 and 17 to the radiator fittings 19;
- - detach hoses:
- - unscrew three screws 24 securing the radiator cover and remove cover 21 with gasket 20;
- - remove the heater core 19 from the housing 11.
The heater core is installed in the reverse order.
To remove the valve 22 of the electric heater, loosen the clamps securing the hoses to the heater valve, disconnect the hoses and remove the valve, after disconnecting the power harness.
Installing the faucet is done in the reverse order.
To remove the electric fan - you need to open the lid of the glove box on the instrument panel.
Unscrew the four screws securing the glove box and remove it together with the cover from the instrument panel socket.
Then unscrew the two screws 15 securing the electric fan cover and remove it from the heater body.
Disconnect the electric motor connection wire 14 (disconnect the wiring block), remove the electrical wire seal 13 and remove the electric fan from the heater housing. Installation of the electric fan is carried out in the reverse order.
In order to remove the control panel, the instrument panel must be removed.
Violation of the distribution of air flows from the OVU
Another cause of air distribution failure is the incorrect position of the dampers in air distributors 5 and 9.
To eliminate this shortcoming, it is necessary: to put the handle 1 in the position of blowing the windshield and side windows, while the lever 2. of the damper axis should be in the extreme right position, and lever 4 - in the extreme left position (clockwise).
If this does not happen, then it is necessary to release the rail(s) 8 and 9 from the latch 5, put the lever(s) in the positions indicated above and fix the rails in the latches again.