Heating of the bus interior and the driver’s workplace is carried out by a liquid heating system that uses the heat of the engine cooling system and a liquid heater
Interior heaters have two operating modes - full and partial. They are controlled using two-position keys located on the instrument panel.
For effective heating of the interior and blowing of windshields, it is necessary to maintain a sufficiently high temperature of the coolant in the engine cooling system and ensure circulation of the liquid through the pipelines, which is achieved by operating a liquid heater and circulation pump, which must be constantly on.
Webasto (Spheros) liquid heaters of the Thermo E200 and Thermo E320 models are installed on PAZ-32053-07 and PAZ-4234 buses, respectively
Installing the Thermo E heater
The heater is secured using four M8 bolts
If necessary, use a backing ring in accordance with Din
Type plate
The type plate is located in a place protected from damage, and if the heater is installed in a vehicle, the type plate must be clearly visible (otherwise a duplicate plate must be used)
On the type plate indicating the type of heater there must be a non-removable marking of the year of its first commissioning by removing inappropriate years from the plate
Liquid heaters of the Thermo E200 and Thermo E-320 models are an autonomous heating system that operates independently of the engine.
The heater is designed to maintain the temperature of the liquid (antifreeze) within limits sufficient for heating the interior, defrosting windshields, and preheating the engine.
When the liquid in the boiler is heated to 85 °C, the heater automatically turns off. When the antifreeze cools to 72 °C, the heater turns on.
A description of the heater is contained in its operating manual, which is included in the delivery package of the bus.
Switching on and starting the heater
Attention! Before turning on the heater, you should make sure that there is a sufficient amount of liquid in the expansion tank and check the position of the valve valves of the bus heating system.
The taps must be in the open position before starting.
When the heater is turned on, the operation indicator lights up, the control unit starts normal operation mode and checks the coolant temperature.
If the coolant temperature is below the upper temperature threshold, the pre-start phase begins.
The combustion air blower and circulation pump are switched on.
After approximately 12 seconds (pre-start time), a high voltage ignition spark appears.
About a second later, a solenoid valve in the fuel pump opens and incoming fuel is injected through the high-pressure atomizing nozzle into the combustion chamber.
In the combustion chamber, fuel is mixed with air. This air-fuel mixture is ignited by the ignition spark and burns in the combustion chamber.
Flame control is carried out by a flame sensor built into the control unit.
Approximately 5 seconds after recognizing the flame, the control unit turns off the pilot discharge generator. Until this moment, the flame has stabilized and the heater is not yet in heating mode.
Operation in heating mode
After the flame has stabilized, the heater operates in normal operation mode. When the upper switching threshold is exceeded, operation in the on mode warming ends and the purging phase begins.
The solenoid valve closes and the flame goes out, but the combustion air blower and circulation pump continue to operate.
After approximately 120 seconds, the combustion air blower is switched off and the purge phase ends.
The heater stops (break in operation). The operation indicator is on.
The heater resumes operation in combustion mode when the lower switching threshold is exceeded. The same operations are performed as when turned on
Temperature control
If the coolant circulation rate is insufficient or the cooling circuit is not properly bled, the temperature may rise too quickly when operating in heating mode.
The control unit recognizes that the temperature is rising too quickly and automatically sets the upper switching threshold to lower values.
The faster the temperature rises, the lower the switching threshold is set to start the interruption. Restarting the burner
after a break in operation is also carried out at a lower switching threshold.
This prevents the overheating protection from tripping due to residual heat.
If the temperature rise (temperature gradient) is again within the permissible limits, the switching thresholds are again set to the normal values (lower switching threshold 72 °C, upper switching threshold 85 °C).
Shutdown
When the heater is turned off, the combustion process ends. The operation indicator goes out and the purge phase begins.
The solenoid valve closes, the flame goes out, and the combustion air blower and circulation pump continue to operate.
After approximately 120 seconds, the combustion air blower is switched off and the purge phase ends.
If a problem occurs during the purge phase (for example, flame detection), the purge phase may last less than 120 seconds. During the purge phase, the heater is allowed to be switched on again.
After a purging phase of 30 seconds and a subsequent pre-start phase, the burner starts again.
Instructions for use and maintenance
Attention! Maintenance and repair of the heater must be carried out by qualified specialists who have undergone in-house training at the heater manufacturer (Spheros and Webasto).
Before opening the heater, it should be disconnected from the on-board network of the bus. The heater should always be disconnected from the bus's on-board power supply before disconnecting the temperature sensor plug.
Performing the disconnection in the reverse order results in AUTOMATIC LOCKING of the heater.
Before disconnecting the burner from the heat exchanger, disconnect the temperature sensor plug.
The temperature in the heater area should not exceed 85 °C (maximum operating temperature).
Exceeding the temperature can cause heater malfunctions and irreversible damage to electronic equipment.
Electrical cables must not have insulation damage (for example, as a result of pinching, heat exposure, kinks, abrasion, etc.).
The temperature sensor cable must not be subjected to mechanical stress (do not pull the cable, do not carry the heater by it, etc.).
It is prohibited to use the heater without exhaust gas extraction in enclosed spaces (garages or workshops), even if the time has been preset, due to the danger of poisoning and suffocation.
This also applies to operation in combustion mode when adjusting the CO2 indicator in the exhaust gases.
It is prohibited to operate the heater near flammable materials (leaves, dry grass, paper, cardboard, etc.).
When operating without coolant (overheating!), the heater casing may reach the ignition temperature of diesel fuel!
Dripping or evaporating fuel must neither collect nor ignite on hot parts or electrical devices.
The air intake and exhaust pipe openings must be checked regularly and cleaned if necessary.
At gas stations and at refueling installations, the heater should be turned off due to the risk of explosion.
In places where flammable vapors or dust may form (for example, near fuel, coal and wood dust, granaries, etc.), the heater should be turned off due to the risk of explosion.
The coolant in the heating circuit must contain at least 20% antifreeze.
When carrying out electric welding work on a bus, to protect the heater control unit, it is necessary to disconnect the main electrical cable (plus) from the battery and ground it to the body.
In case of deviations from normal operation, the heater is automatically blocked.
There are two types of heater blocking - emergency blocking in case of malfunctions and blocking.
The interlocks are designed to protect the heater from damage primarily due to unacceptable thermal loads.
Thermal stress can occur for the following reasons:
- a) coolant circulation rate is too low;
- b) insufficient amount of coolant (dry overheating);
- c) failure of the circulation pump.
When the heater is blocked, depending on the time of occurrence, the purge phase can last up to 120 seconds. The reason for blocking can be determined using the indicator's flashing pulses.
Problems when turning on and during startup
The heater is in emergency blocking mode. The engine stops immediately or does not start.
Problem criteria:
- 1) Short circuit or interruption of electrical components:
- a) burner motor (stops immediately);
- b) ignition discharge generator;
- c) additional nozzle heating system.
- 2) Interruption of the circulation pump.
- 3) Flame detection or premature detection of flame by the flame sensor before the high voltage ignition spark is turned on.
- 4) No start: no flame recognition up to 15 seconds after opening the solenoid valve.
- 5) The temperature sensor produces unacceptable temperature values.
- 6) Operating the heater outside the permissible operating temperature range.
- 7) When starting the engine or exceeding 20 seconds from the time of the heating request, the lower voltage threshold of approximately 20.5 V is not reached.
- 8) Exceeding the upper voltage threshold of approx. 30 V when starting the engine or exceeding 6 seconds (purge phase only, no fault lockout).
Problems when operating in heating mode
If there is a problem with the heating mode, it will first switch to a 120 second purge phase. After this, the heater goes into emergency blocking mode.
Problem criteria:
- Short circuit of the circulation pump
- Short circuit or interruption of other electrical components (motor, solenoid valve, pilot generator, injector heating system)
- Water temperature is above the upper switching threshold.
- The temperature sensor produces unacceptable temperature values.
- Operation of the heater outside the permissible operating temperature range.
- Flame interruption (interruption of combustion for more than 15 seconds).
- When starting the engine or exceeding 20 seconds from the time of the heating request, the lower voltage threshold of approximately 20.5 V is not reached.
- Exceeding the upper voltage threshold of approximately 30 V when starting the engine or exceeding the duration of 6 seconds (only the purge phase is performed without emergency blocking).
- Control unit error.
Problems during the purging phase
Causes of the problem:
- Short circuit or interruption of the burner motor (stops immediately).
- Interruption of the circulation pump.
- Operation of the heater outside the permissible temperature range.
- When starting the engine or exceeding 20 seconds from the time of the heating request, the lower voltage threshold of approximately 20.5 V is not reached.
- Exceeding the upper voltage threshold of approximately 30 V when starting the engine or exceeding the duration of 6 seconds (only the purge phase is performed without emergency blocking).
- Control unit error.
Cancel emergency blocking and delete error
The problem is cleared when the heater is turned off. After this, it is immediately ready to start again.
Attention! If blocking occurs several times in a row due to malfunctions, the heater is blocked.
Attention! Only personnel trained by Spheros (Webasto) are allowed to remove the heater blockage.
If a malfunction occurs, you must first check the condition of the fuses, plug connectors and heater wiring, the condition of the battery pole terminals and eliminate any defects found.
Attention! Error detection should be performed before replacing the fuse.
The heater should be disconnected from the on-board network and the fuse should be replaced in a de-energized state. The correct size fuse must be used.
After replacing the coolant, carefully remove air from the cooling system.
Incomplete air removal may result in problems caused by overheating during heating operation.
A sign of high-quality air removal is the almost silent operation of the circulation pump.
Bleeding the cooling circuit
Open the taps, open the air bleed valves on the heaters.
Pour in coolant until it appears in the taps on the heaters, close the taps and add liquid to the maximum mark.
Start the engine at high idle speed.
After opening the engine thermostat, turn off the engine and check the coolant volume; add coolant if necessary.
With the engine off, turn on the heater with the circulation pump and the bus heater fan.
After the bus engine cooling time has expired, the heater should turn on automatically, and after reaching the upper switching threshold, it should limit its performance.
If the heater does not turn on automatically, you should check whether the heater overheating protection has tripped and whether the heater is blocked.
Unlock the heater and repeat the air removal procedure.
The diagram of the microclimate system of the PAZ-4234, PAZ-32053-07 bus is shown in Figure 3
Webasto liquid heater model DBW 160.02
The Webasto liquid heater model DBW 160.02 can be installed on the PAZ-32053-07 bus.
The heater model DBW 300.59 can be installed on the PAZ-4234 bus.
The Webasto liquid heater is an autonomous heating system that operates independently of the engine.
The heater in combination with the engine cooling system is designed to heat the interior, defrost windshields, and preheat the engine.
Turning on the heater
When the heater is turned on, the LED indicating the heater operating modes lights up, and the combustion air blower 16 (Fig. 3), the fuel pump 17 and the coolant circulation pump begin to operate.
Heater diagram: 1 - fan electric motor; 2 - coupling; 3 - high-voltage voltage source; 4 - gear transmission; 5 - burner body; 6 - tip of the ignition electrode; 7- electromagnet; 8 - ignition electrode; 9 - nozzle; 10 - combustion chamber; 11 - thermal fuse; 12 - temperature sensors; 13 - heat exchanger; 14 - casing; 15 - fan housing; 16 - fan impeller; 17- fuel pump; 18-electric heater; 19 - flame indicator; A - liquid outlet pipe; B - air suction pipe; G - gas outlet pipe; F - liquid inlet pipe; T - fuel line
After approximately 15 seconds, the magnetic valve 7 opens and fuel is injected through the nozzle 9 into the combustion chamber 10, where due to the action of a simultaneously switched on high-voltage ignition spark between the electrodes 8, the fuel ignites.
After the formation of a flame, the flame indicator 19 turns off the ignition spark sensor.
Heating mode
When the heater reaches operating temperature, the heating control thermostat takes over control of the heater operating modes.
Due to alternating switching on and off, the coolant temperature is maintained at a constant level.
If the temperature in the heating circuit rises above the upper switching point, the solenoid valve closes, thereby stopping the fuel supply, causing the flame to die out.
The heater's after-run purge mode begins, during which the combustion air blower and circulation pump continue to operate for another 150 seconds, after which they are automatically switched off.
During the regulation pause, the circulation pump continues to operate, the indication of the heater operating modes lights up.
If the temperature in the heating circuit falls below the lower switching point, a new heater start process begins.
Shutdown. When the heater is turned off, the combustion process stops. The heater operating mode indication goes out and the heater purge mode begins.
The combustion air blower and circulation pump are switched off after approximately 150 seconds. Restarting the heater during the purge mode is allowed.
When the heater is turned on during its purge on the run-out after operation, the purge mode is interrupted and a new start occurs.
Fuel consumption for full load DBW 160 - 2 l/h, DBW 300 - 4 l/h.
Instructions for use and maintenance
- Due to the danger of poisoning and suffocation, the heater cannot be turned on (including with a programmable timer) in enclosed spaces (for example, in garages) if there is no hood. At gas stations, as well as wherever I can If flammable vapors and dust do not form (near fuel, coal, wood or grain warehouses, etc.), the heater must also be turned off.
- The air intake and exhaust pipe openings should be checked regularly and cleaned if necessary.
- For preventive maintenance, the heater should be turned on monthly for 10 minutes with a cold engine and the car’s fan power at minimum, and checked once a year, no later than the beginning of the heating season, at the Webasto service.
- If there is strong smoke, unusual noises or the smell of fuel, the heater must be turned off immediately, locked by removing the fuse, and checked at a Webasto service station.
- The temperature around the heater control unit should not exceed 85°C, otherwise irreversible damage to its electronics may occur.
- The coolant must contain at least 10% of approved brands of antifreeze, its level in the circuit must correspond to the norm. When updating the coolant, it is necessary to carefully remove air from the cooling system and from the heater by turning on its circulation pump (if there is a separate pump switch) or the heater itself and after 15...20 seconds turning it off.
- When carrying out electric welding work on a bus, to protect the heater control unit, it is necessary to disconnect the main electrical cable (plus) from the battery and ground it to the body.
- Before the start of the heating season, you need to replace the fuel filter.
- Diesel fuel is used as fuel. The fuel must retain its ability to be filtered at any operating temperature. When switching to winter fuel, it is necessary to turn on the heater for 15 minutes before operating the heater so that the fuel lines are filled with new fuel.
If a malfunction occurs, you need to check all fuses and plug connectors of the heater and eliminate any defects found.
If the operation indicator on the switch does not light up when the heater is turned on, check and, if faulty, replace the fuse.
If the indicator lights up, but goes out after about 30 seconds, check the fuse and, if faulty, replace it or press the heat limiter button.
If overheating, eliminate the cause of overheating and then:
- - replenish the coolant to the prescribed volume;
- - replace the temperature fuse with the same one (color-coded);
- - or return the heating limiter button to its previous position.
Note: Before replacing the temperature sensor or temperature fuse, you must relieve excess pressure in the cooling system by opening the radiator cap.
You can remove a blockage that occurs as a result of a malfunction by turning the heater off and on again.
If these measures do not resolve the malfunctions, the heater must be submitted to an authorized Webasto service station.
The search for causes of malfunctions in the Webasto heater is carried out using the quick diagnostic table below.
The table is based only on obvious, clearly identifiable symptoms of malfunctions and therefore cannot replace the detailed knowledge of specialized workshops.