FAQ
TL;DR: If your Scania R420’s Eberspächer Airtronic D4 beeps then stops, the fix is usually the fan motor; these heaters are rated ~2,500–3,000 hours. “99 percent of the engine and the burner are to be replaced.” [Elektroda, SP7SEC, post #16948312]
Why it matters: This FAQ helps drivers and techs quickly decode ATA errors and choose the fastest fix without guesswork.
Quick Facts
- ATA 120 = glow plug circuit short; glow plug ≈ 2 Ω when good. [Elektroda, mariomalinie, post #16935637]
- ATA 133 = combustion air fan impeller not moving/incorrect RPM; motor often needs replacement. [Elektroda, mariomalinie, post #16939167]
- Symptom pattern: fan attempts multiple short starts, no fuel-pump ticks, then “heater error.” [Elektroda, pompa354, post #16943843]
- Typical service life: manufacturer guidance ~2,500–3,000 operating hours before major parts. [Elektroda, SP7SEC, post #16948312]
- Confirmed fix from thread: replacing the fan motor restored normal heat. [Elektroda, pompa354, post #17269624]
What does ATA 120 mean on an Airtronic D4, and how do I confirm it?
ATA 120 flags a short circuit in the glow plug circuit. Pull the glow plug and measure resistance at room temperature; about 2 Ω indicates a healthy element. Replace the glow plug if shorted or out of spec, clear codes, and retest the start cycle. “A short circuit in the glow plug circuit. Resistance about 2 Ohm.” [Elektroda, mariomalinie, post #16935637]
What does ATA 133 mean and what usually fixes it?
ATA 133 means the combustion air fan impeller is not moving correctly. Causes include blockage, over‑speed sensing, or a missing rotor magnet. The common corrective action is replacing the fan motor assembly and inspecting for debris. Many shops treat motor replacement as the durable fix. [Elektroda, mariomalinie, post #16939167]
My heater’s fan starts repeatedly but the fuel pump never clicks—why?
The controller won’t pulse the fuel pump until it verifies proper fan RPM and airflow. Repeated brief high‑speed spins followed by a fault usually trace to the fan motor or its sensing. Fix the fan issue first; fuel delivery resumes once conditions pass checks. [Elektroda, pompa354, post #16943843]
Can worn brushes cause start–stop behavior on the Airtronic D4 fan?
Yes. Low or uneven brushes can make the fan run intermittently, fail to reach target RPM, and then fault. A temporary tap may revive it briefly, but replacement is the reliable fix. “After hitting the engine, it works for some time.” [Elektroda, mariomalinie, post #16943804]
The fan runs fine on a 1.5 V battery—could the controller be locked out?
The thread raised lockout as a possibility but did not confirm a DIY unlock. Bench tests at 1.5 V don’t validate RPM sensing under load. Use proper diagnostics and address fan motor condition first before suspecting lockout. [Elektroda, pompa354, post #16943012]
How long do these heaters typically last before major parts are due?
One experienced poster cites manufacturer guidance of roughly 2,500–3,000 operating hours for engine/burner replacement. Plan maintenance around that figure to avoid in‑season failures. This is a practical lifecycle statistic for fleet planning. [Elektroda, SP7SEC, post #16948312]
What ultimately fixed the OP’s Scania R420 heater in this thread?
Replacing the fan motor solved the repeated start attempts and restored normal operation. The owner confirmed the brushes were worn down and reported the heater works fine after motor replacement. [Elektroda, pompa354, post #17269624]
Are ATA 112 or ATA 148 explained in this discussion?
No. The original post lists ATA 112 and ATA 148 alongside 120, but only 120 and 133 were decoded here. Use a service tool or manual for 112/148 specifics. [Elektroda, pompa354, post #16917905]
What quick checks should I do for a no‑heat with beeps on Airtronic D4?
Check glow plug resistance near 2 Ω, inspect wiring for shorts (ATA 120). Listen for fan spin‑ups; if it cycles then faults, suspect the fan motor (ATA 133). Do not expect fuel‑pump ticks until the fan passes RPM checks. [Elektroda, mariomalinie, post #16935637]
Is replacing the fan motor a long‑term fix?
Yes. A veteran tech says replacing the motor plus inspection and cleaning resolves recurring faults for years. This approach prevents marginal RPM from triggering new errors. “Replace the engine plus inspection and cleaning…and the topic ends.” [Elektroda, mariomalinie, post #16944508]
How do I clear repeated fan‑related faults the straightforward way?
- Replace the combustion‑air fan motor with a quality part.
- Inspect and clean the entire heater assembly and burner.
- Clear codes and run several full heat cycles to verify stable RPM.
“Replace the engine plus inspection and cleaning…” [Elektroda, mariomalinie, post #16944508]
Why does the heater attempt up to fifteen brief starts, then quit?
That pattern points to the controller trying to validate fan RPM multiple times. After repeated failures, it throws a heater error and halts without fueling. Address the fan motor and airflow path to stop the loop. [Elektroda, pompa354, post #16943843]
What is the Eberspächer Airtronic D4 in simple terms?
It’s a 24 V diesel-fired air heater used as an auxiliary/parking heater. It burns small amounts of fuel to heat cabin air and runs an electric fan for airflow. The thread covers common D4 faults and fixes. [Elektroda, pompa354, post #16917905]
What is an ATA code in this context?
ATA codes here are heater fault indications shown on the controller/remote. They map to specific subsystems like the glow plug or fan. In this thread, ATA 120 and 133 were decoded and resolved. [Elektroda, pompa354, post #16917905]
the fan starts fifteen times and squeaks again and a heater fault pops up. The fuel pump does not get an impulse and it seems to me that it is working, because when connected to the rectifier, you can hear that it speaks. Please, give me some hint what this error is
