Eberspächer shows 011: the heater is not getting enough voltage
Updated: 2026-11-10
In short. Code 011 is not about the burner or the fuel: the control unit received too little voltage and shut the heater down. Start with the fuses, the power wires, the ground and the positive battery terminal.
What the unit actually records
In the Eberspächer factory table, 011 is undervoltage with shutdown. The condition is simple: the voltage at the control unit stayed low for at least 20 seconds in a row. A brief dip does not set the code.
The thresholds differ slightly between manuals:
| Heater | System | Code is set if voltage is |
|---|---|---|
| Hydronic | 24 V | below 19 V |
| Airtronic 2 and 4 (Espar manual) | 12 V | below 10.2 V |
| Airtronic 2 and 4 (Espar manual) | 24 V | below 20.4 V |
How the code looks on different controllers
The same fault is shown differently, so you will not see "011" everywhere:
| Controller | What the driver sees |
|---|---|
| Old modular timer 1531 | A three-digit number 011 marked AF (active fault) or F1-F5 (from memory) |
| EasyStart Pro | No number: a red flashing ring on the button and the text "Undervoltage" |
| EasyStart Select | No number: an icon meaning "heater off, undervoltage" |
Neighbouring codes people mix up with 011
| Code | Meaning | Condition |
|---|---|---|
| 011 | Undervoltage, shutdown | low for at least 20 s in a row |
| 010 | Overvoltage | above 16 V (12 V system) or above 32 V (24 V system), at least 20 s |
| 012 | Overheat at the overheat sensor | a different cause, not related to power |
| 091 | External interference voltage | noise in the supply, not a sag |
Details for each: 011, 010, 012, 091.
What to check without instruments
For code 011 the factory names four checks; do them in this order:
- The fuses in the heater circuit.
- The power wires to the heater: breaks, corrosion, damaged insulation.
- The negative connections (ground): tight and clean.
- The positive battery terminal: corrosion and a firm contact.
Everything else is measuring and replacing parts.
When to go to a workshop
- the code returns after the fuses, wires, ground and terminal have been checked;
- the voltage at the heater connector has to be measured: per the manual it should equal the battery voltage, and that measurement is a workshop job.
Questions and answers
How is 011 different from 010?
011 means there is too little voltage, 010 too much (above 16 V on a 12 V system and above 32 V on a 24 V system). Both are set if the condition lasts at least 20 seconds.
Why does my controller not show 011?
EasyStart Pro shows a red flashing ring and the word Undervoltage instead of a number, EasyStart Select shows an icon. The old modular timer 1531 shows the three-digit number.
Does it mean the heater is broken?
Not necessarily. The code is about the supply, not the burner or the fuel: the cause is usually a fuse, wiring, ground or the battery terminal.
What voltage should be at the heater connector?
According to the factory manual, the same as at the battery. Measuring it is a workshop task.
Code pages on the site
- Code 011 Eberspächer - code page
- All Eberspächer codes
- Index of heater codes
Checked against manufacturer manuals and tables; the same facts as in our videos and articles. The decision to drive remains with the driver.
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