Is your parking heater smoking, noisy or refusing to start?
Does heavy smoke always mean a faulty glow plug? Why does a heater lock out, and which sounds are normal?
We have put together the signs of parking heater problems, their possible causes and advice on when to contact a workshop. Find out what to watch for so heating problems do not catch you out on a cold night.
Why a parking heater smokes, makes noise or will not start
A warm cab is important for both work and proper rest. But if your parking heater starts smoking, makes unfamiliar sounds or refuses to start, the question is whether it needs servicing or a repair.
The following covers common symptoms and possible checks for diesel-powered independent air heaters. One symptom alone is not enough for an accurate diagnosis: the heater model, fault code and the stage of operation at which the problem occurs all matter.
The heater produces heavy smoke
White or light-coloured smoke together with a failed start may be associated with a sooted-up burner or a problem in the ignition assembly. For example, Eberspächer technical information describes excessive white smoke and failed starts when excessive carbon deposits have formed in the combustion assembly. A workshop checks the burner, glow plug and its screen, as well as the fuel supply. Smoke colour alone does not mean that the glow plug needs replacing. [1, 2]
Black smoke and soot are reasons to check the combustion air supply and exhaust path. A blockage may interfere with combustion; fuel metering should also be checked. Incorrect installation may also play a part if it allows exhaust gases to be drawn back into the combustion air intake. [2, 3]
Do not try to resolve persistent or heavy smoke by repeatedly switching the heater on. The cause must be identified first.
The heater has become louder
Not every sound indicates a fault. Rhythmic ticking from the fuel pump is normal on some models, but how clearly it can be heard depends on the pump mounting and vibration transmitted to the vehicle body. AUTOTERM mentions this in its installation instructions, for example. [4]
New squealing, scraping or pronounced vibration needs a different assessment. Possible checks include whether the fan rotates freely, whether the blades touch the housing, contamination and the condition of the motor bearings. An audio recording may help the workshop, but inspection is needed to establish a component’s condition. [2, 3]
If unusual combustion noise occurs together with heavy smoke or a smell of fuel, stop using the heater. [5]
The heater starts and stops, or does not begin heating
The burner itself is not always at fault. Possible causes include an inadequate power supply, voltage drop at connections, an interrupted fuel supply or overheating. A blocked heated-air intake or warm-air outlet—for example, a bag placed against a grille—can contribute to overheating. [2, 6]
It is important to distinguish between two air paths: air used to heat the cab and combustion air. A restriction in one can cause overheating; a restriction in the other can cause combustion problems.
A battery reading taken at rest does not rule out a power-supply problem. The voltage measured at the heater itself during start-up also matters for diagnosis. [2]
What heater lockout, or lock mode, means
Lockout is a protective response. Depending on the model and fault, the heater may stop the current operating cycle or enter a more persistent lockout that prevents another start. Repeated failed starts, flame failure or overheating may trigger this. [3, 6]
Clearing a lockout does not, by itself, fix the cause of the fault. First establish why the protection was triggered. Only then should the heater be returned to operation in accordance with the instructions for that particular model. Some heaters or vehicle-integrated systems require a diagnostic tool. [3]
That is why the universal advice to “pull the fuse and try again” is not suitable for every heater. Identical fault-code numbers on different models cannot automatically be interpreted in the same way either.
What to check before contacting a workshop
You can gather useful diagnostic information without dismantling the heater:
Check the fuel level and the condition of the heater fuses in accordance with the vehicle manual.
Make sure the heater air grilles in the cab are not covered.
Write down or photograph the fault code and heater model.
Note when the problem occurs: immediately after switching on, after a few minutes or after a longer period of operation.
Describe any smoke, unusual smell or sound you have noticed.
For safety, do not repeatedly run a faulty heater just to record the symptom. These checks help the workshop begin targeted diagnostics; they do not replace professional diagnosis. [6]
When must you stop using the heater immediately? If there is persistent heavy smoke, a smell of fuel or unusual combustion noise, stop using the heater and follow the emergency shutdown instructions for that model. If exhaust gases enter the cab, move into fresh air and do not use the heater until it has been checked. [5, 8]
For a normal shutdown, use the control unit and allow the run-on cycle to finish. An emergency may require a different procedure: for example, Webasto specifies disconnecting the heater by removing the fuse when certain hazardous symptoms occur. Normal shutdown and emergency disconnection are therefore not the same procedure. [5]
Servicing before cold weather helps identify problems early
Before the season of intensive use, it is worth checking the heater’s operation and arranging servicing in accordance with the manufacturer’s instructions. The work required depends on the model, operating hours and condition: there is no single universal interval suitable for every heater. [5, 7]
Depending on the model, servicing includes checking fault history, air and exhaust paths, fuel-system leak-tightness, electrical connections and the condition of the combustion assembly. Cleaning or component replacement is carried out where necessary. [7]
Is your parking heater smoking, noisy or refusing to start? Book parking heater servicing or repairs at Greenway Serviss. When booking, provide the vehicle and heater models, fault code and the symptoms you have noticed.
Greenway Serviss · Zemeņu iela 2i, Jelgava
Telephone: +371 22545322
Technical sources
Eberspächer Airtronic D2 and D4 technical bulletin on carbon deposits in the burner. Copy of the manufacturer’s technical material.
Eberspächer Airtronic D2 and D4 technical and repair documentation. Copy of the manufacturer’s manual.
Webasto Air Top 2000 STC workshop manual. Copy of the manufacturer’s manual; lockout, troubleshooting and fan inspection.
AUTOTERM AIR installation and operating instructions. Fuel-pump noise and mounting.
Webasto Air Top 2000 STC operating instructions. Safety, shutdown and maintenance.
Eberspächer Airtronic S2 and M2 instructions. Protective functions and initial checks.
Eberspächer Airtronic 3 technical description. Safe exhaust-gas routing.