Eberspacher Heater Not Starting? Fault Code 052 (P00012A) Fix – Airtronic S2 D2L

Written By: Muhammad Khalid

23 Apr 2026

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REF: MV/250103

SUBJECT: EBERSPACHER DIESEL HEATER NOT STARTING? FAULT CODE 052 (P00012A) FIX – AIRTRONIC S2 D2L

 

We recently had a van owner call our tech support line because their Eberspacher heater was refusing to ignite. If you are seeing Fault Code 052 (or the modern communication code P00012A) on your Airtronic S2 D2L, it simply means the unit failed to ignite during the start-up phase.

One of our customers in the US recently asked why their fan kept running even after the heater failed to start. We explained that if a flame is not detected within 90 seconds, the heater automatically attempts a second start. If that fails too, the fuel is cut off and the fan runs for about 4 minutes to ventilate the combustion chamber and clear out any unburned vapours. This vital safety process is handled by the PT1000 flame sensor, which must send a stable signal to the control unit to keep the heater running.

 

How to Fix Eberspacher Fault Code 052

We keep receiving questions about this specific "no-start" issue. After discussing these common failures with an Eberspacher engineer who visited us recently, we recommend following this step-by-step diagnostic process to find the culprit.

1. Check the Fuel Supply System

A common issue we see in the workshop is air entering the system through a loose connection.

  • Visually Inspect: Check your fuel pipes for leaks or physical damage.
  • Check Connections: Ensure every hose connection is tight, as even a small gap can allow air ingress.
  • Filter Maintenance: Do not forget to check the integrated filter strainer in the fuel pump, along with any additional fuel filters you have installed.

2. Confirm Metering Pump Operation

Fuel delivery typically begins 60 seconds after activating the heater. If ignition fails, delivery stops automatically after about 90 seconds.

Use a multimeter to measure the pump resistance:

  • 12 V: 9.5 Ω ± 0.5 Ω
  • 24 V: 36.0 Ω ± 1.8 Ω

3. Test the Glow Plug

The glow plug is critical for ignition. When applying 9.5 V ± 0.1 V, the current draw after 25 seconds should be:

  • 9.5 A (+1 / −1.5 A)

Typical resistance values:

  • 12 V: 0.42 Ω – 0.70 Ω
  • 24 V: 1.2 Ω – 2.0 Ω

Wiring Check:

Inspect for continuity, shorts, or any visible damage.

4. Test the Flame Sensor (PT1000)

The flame sensor acts as the "eyes" of your heater; if it does not detect the heat from a successful ignition, the control unit will immediately trigger a shutdown. To verify its health, measure the resistance across the sensor leads:

Reference values:

  • 1000 Ω at 0 °C
  • 1078 Ω at 20 °C

Wiring Check:

Always inspect the sensor harness for continuity, loose terminals, or heat damage to the insulation.

5. Inspect the Glow Plug Screen (Strainer)

We recently helped a customer whose heater would not fire despite having a brand-new glow plug. The issue was a clogged glow plug screen (or strainer) inside the burner. This small mesh screen is essential for properly atomising the fuel during ignition.

  • Light Sooting: Clean the screen socket lining with a suitable cleaning agent to restore proper airflow.
  • Heavy Carbon Build-up: If there is significant carbon build-up, the glow plug lining must be replaced to ensure proper fuel delivery.

6. Combustion Air and Exhaust

Finally, ensure your exhaust system is clear of dirt or snow. Make sure exhaust gases are not being drawn back into the combustion air intake and that all pipes are within Eberspacher’s installation parameters.

Still having trouble getting your S2 D2L to fire up? We love helping our community solve these puzzles. If you need help with a resistance reading or finding the right replacement part, contact the Butler Technik team today!

                                                                                                                                                                                                                                     
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Matthew Varlow David Butler
Technical Support Director
Article Link: Eberspacher Heater Not Starting? Fault Code 052 (P00012A) Fix – Airtronic S2 D2L 
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