Stationary heater (STH) diagnosis, function check

AD83.70-P-3003A

Stationary heater (STH) diagnosis, function check

12.8.97

 Danger!

Risk of explosion due to fuel vapors, risk of poisoning from inhaling combustion gases and risk of injury from burns during or after heater operation.

Do not put stationary heater, auxiliary heater or engine with heater booster into operation in confined spaces or while refueling. Allow heater unit to cool down after operation and wear safety gloves.

AS83.70-Z-0002-01A



Heater booster unit (STH) diagnosis, advanced information

AD83.70-P-2001A

Air inlet of heating and ventilation system must be clear, remove any foreign bodies, such as leaves, if necessary.

The vehicle heater must be set to "MAX" position.

Check coolant circuit. The coolant circuit must be adequately filled with coolant and bled carefully. Coolant lines must not be kinked or pinched.

Coolant temperature  20°C

Battery voltage 11-14 V

Function check

Scope of test

Operation/Requirement

Specified value

Remedy

1

Switch on stationary heater

Press instant heat button  on stationary heater timer.

The green indicator lamp on the timer illuminated, circulating pump and combustion air blower start up; audible operating noise and detectable air flow at exhaust gas outlet

Coolant temperature < 59°C

Heater circuit thermostat shuts off the entry to the vehicle cooling and heating circuit, and for a more rapid increase in temperature at the heater, initially only permits a short circulation of the coolant which runs from the heater via the heater unit and recirculating pump.

AD83.70-P-4002A

AD83.70-P-5001A

2

Fuel delivery starts after approx. 40 seconds and combustion air blower is switched off for 3 seconds

Fuel metering pump cycles audibly

AD83.70-P-4002A

AD83.70-P-5001A

3

The combustion air blower is switched on again and the cycling frequency of the fuel metering pump is reduced simultaneously

Operating noise of combustion air blower and slower cycling noise of the fuel metering pump is audible

AD83.70-P-4002A

AD83.70-P-5001A

4

The speed of the combustion air blower is increased in 2 stages within 120 seconds, combustion starts and fuel delivery is increased

Audible increase in combustion air blower speed and cycling noise of fuel metering pump and exhaust gas flow heats up detectably at the same time

AD83.70-P-4002A

AD83.70-P-5001A

5

Combustion starts and stabilizes

The combustion air blower and fuel metering pump deliver audibly at their maximum speed or output in full load operation, coolant temperature increases.

Coolant temperature in cooling and heating circuit > 30°C:

The vehicle heater blower starts up; audible operating noise and detectably warmer air flow in interior

Coolant temperature exceeds 59°C:

Heating circuit thermostat opens up the path for the coolant flow to the vehicle's cooling and heating circuit, heat exchange starts in the heating heat exchanger for heating up the interior

AD83.70-P-4002A

AD83.70-P-5001A

6

Switching off stationary heater

Press instant heat button  on the timer

The green indicator lamp on the timer goes out, the vehicle heater blower and fuel metering pump are switched off immediately. The air flow in the interior is no longer detectable and the cycling noise of the fuel metering pump is no longer audible.

AD83.70-P-4002A

AD83.70-P-5001A

7

Heater unit run-on

starts

From part-load operation  Run-on for approx. 110 seconds

From pull-load operation  Run-on for approx. 175 seconds

Circulating pump and combustion air blower continue operating; audible operating noise and air flow, which is slowly cooling down detectably, at exhaust gas outlet

AD83.70-P-4002A

AD83.70-P-5001A

8

Run-on terminates

Operating noise of circulating pump and combustion air blower no longer audible, detectable lack of air flow at exhaust gas outlet

AD83.70-P-4002A

AD83.70-P-5001A