Diesel Heater Troubleshooting: No Error Code Displayed

If your diesel heater is showing an error code, please refer to our Diesel Heater Error Codes Guide for specific solutions.

If there is no error code and your heater still won’t start, blows cold air, or behaves oddly, this guide covers the most common issues and how to fix them.

Quick Links:

It Does Not Turn On

  • Test directly from a fully charged 12V battery. Disconnect any chargers or unstable power sources.
  • Check your fuse. Most models have an inline fuse near the battery connection.
  • Ensure correct polarity on all wires — reversed polarity can cause total shutdown.
  • Inspect wiring harness for any breaks or corrosion.

No Fuel Flow

  • Prime the fuel line by loosening the clamp near the pump and turning the unit on briefly.
  • Check for air bubbles in the fuel line — any air will stop proper flow.
  • Replace the fuel filter if clogged or filled with debris.

Pump Clicks But No Ignition

  • This often means fuel is moving, but combustion isn't happening.
  • Remove and inspect the glow plug — clean if it shows signs of carbon buildup.
  • Check that the combustion chamber is not flooded with diesel from failed attempts.

Fan Spins But No Heat

  • The heater may be stuck in ventilation mode or experiencing a weak glow plug.
  • Ensure the temperature sensor is not disconnected.
  • Test the glow plug or replace if it’s old or covered in carbon.

Heater Blows Cold Air

  • Occurs when the heater is only running the fan without combustion.
  • May also happen during the cool-down cycle at the end of operation — this is normal.
  • If continuous, check the fuel delivery system and glow plug function.

Fan Rubbing or Grinding Noise

  • Usually caused by bent fan blades or debris inside the housing.
  • Open the unit and spin the fan by hand to detect rubbing points.
  • Re-centre or carefully bend the fan blades back to original position if deformed.

Black Smoke From Exhaust

  • Indicates incomplete combustion — often due to too much fuel or not enough air.
  • Check glow plug, air intake, and clean the combustion chamber.
  • Using low-quality diesel can also cause excessive soot and smoke.

White Smoke From Exhaust

  • Usually a sign of unburnt fuel vapor — common if the heater fails to ignite.
  • Check the glow plug and ensure fuel lines are not over-primed or flooded.

Strong Fuel Smell But No Start

  • Means diesel is entering the chamber but not igniting.
  • Clean or replace the glow plug.
  • Ventilate the combustion chamber before restarting to avoid over-fuelling.

Blocked Air Intake or Exhaust

  • Make sure nothing is blocking the exhaust pipe or air intake.
  • Bird nests, dirt, snow, or insects can clog the ends of the pipes.
  • Always use the mesh covers supplied with the heater.

Control Panel Unresponsive or Flickering

  • Check the connector between the controller and the mainboard.
  • If using Bluetooth or LCD versions, make sure they are compatible with your model.
  • Try holding the power button for 5 seconds to force reset.

Heater Cycles On and Off Without Running

  • Low voltage is the most common cause. Confirm a steady 12V during startup.
  • Blocked intake or exhaust may cause overheating shut-off.
  • A faulty motherboard may restart the heater repeatedly without completing a cycle.

High Altitude or Freezing Weather Issues

  • Use winter diesel or fuel additives to prevent gelling.
  • Some heaters include a high-altitude setting — enable it if above 1500m.
  • Keep batteries warm and above 12.0V for reliable starting.

Pump Ticking Noise

The ticking sound from the fuel pump is completely normal — it's part of how the pump works to deliver fuel in precise pulses. However, in quiet environments like campervans, sheds, or cabins, it can become quite noticeable.

If you find the noise too loud, here are a few ways to reduce it:

  • Upgrade to a quieter fuel pump designed to reduce vibration and sound.
  • Install a sound-dampening pump case to help muffle the ticking.
  • Mount the pump on a soft surface such as dense foam or rubber instead of directly onto metal or hard surfaces.
  • Keep fuel lines as short as possible and avoid hard plastic clips, which can amplify vibration.
  • Use rubber or silicone mounts to reduce transfer of noise into the vehicle or structure.

Reducing pump noise is optional and mostly a comfort improvement, especially when sleeping close to the unit. If your heater is working well and the ticking is the only issue, there's no fault to worry about.

Still Having Issues?

If your heater still won’t start and no error code is displayed, contact your supplier for further support or consider a diagnostic inspection. And don’t forget — if an error eventually appears, you can check our error code guide here.