| Regulation of auxiliary heaters -B5W- S and -D5W- S |
| The auxiliary heater -B5W- S / -D5W- S is intended to heat the coolant and thereby assist the heating output of the engine. It can also be used as an auxiliary heater when the engine is switched off. |
| Various operating modes can be set depending on heat required in heating circuit: |
| After the engine is started at an ambient temperature of below approx. 10 °C and if the coolant temperature is below approx. 77 °C, the auxiliary heater in vehicles with TDI engines is automatically switched on via the ambient temperature switch -F38-. |
| If the heat required is 5000 watts (100% of heating output), then the heater unit operates in full load mode. The coolant temperature increases up to 85 °C (maximum). |
| The auxiliary heater controls two heating levels: -B5W- S = 5000 watts or 1500 watts; D5W- S = 5000 watts or 2200 watts. |
| The heating levels cannot be set manually. The control unit -J162- controls the heat requirement. |
| The heater control unit -J162- calculates the heat requirement based on the temperatures measured by the coolant temperature sender for heater -G241-. |
| The auxiliary heater reduces its power if the coolant temperature is 85 °C. The heater interrupts control. Then the 130 second run-on phase starts. The combustion air blower -V6- runs at its highest level during the run-on phase. The circulation pump -V55- continues running until the next control start. |
| The control start begins at a coolant temperature of 65 °C at the highest level and the highest speed of the combustion air blower -V6-. |
| If the heater unit is switched off or if a malfunction shut-off occurs, the run-on phase of the combustion air blower -V6- takes place at low speed. |
| The flame is monitored by the flame monitor -G64-, the maximum permitted temperature is monitored by the overheating sensor -G189-. Both influence the heater control unit -J162- which switches off when there are malfunctions. |
| The start is repeated if the heater does not ignite within 90 seconds after fuel pumping starts. A malfunction shut-off occurs if the heater does not ignite after another 90 seconds. |
| A new start is performed initially if the flame goes out by itself during operation. The malfunction shut-off occurs if the heater does not ignite within 90 seconds after the fuel pumping is switched on or if the heater ignites but goes out again. The malfunction shut-off can be revoked by switching off and back on again. |
| The overheating sensor -G189- is triggered in the event of overheating (lack of water, air in the coolant circuit). The fuel supply is interrupted. The malfunction shut-off then occurs. Once the cause of overheating has been eliminated, the auxiliary heater can be restarted by switching off and back on again. Prerequisite: the auxiliary heater has cooled down sufficiently! |
| The malfunction shut-off occurs if the voltage drops below approx. 10.2 volts or rises above approx. 16 volts. |
| The auxiliary heater does not start if the glow plug for heater -Q9- is defective. |
| The speed-controlled combustion air blower -V6- is permanently monitored. The malfunction shut-off takes place in the event of a fault if it does not start or becomes blocked. |
| Check the following in case of a sooty flame: eliminate obstacles to the combustion air supply and in the exhaust gas pipe. Check the quantity delivered by the metering pump -V54-, renew it if necessary. Clean deposits off the heat exchanger for the auxiliary heater, replace if necessary. |
|
|
|
