F00

Webasto Furnace: “F00”

warning RV furnace fault codes

Safety This is a fuel-burning heater with a live exhaust. Never bypass the lock-out repeatedly to force operation - lock-outs exist to prevent unsafe combustion or overheating. Do not run the heater in an enclosed space without a properly routed, sealed exhaust; incomplete combustion can produce carbon monoxide.

What it means

The heater's control unit (ECU) has an internal fault, the heater has been permanently locked out, or the built-in room-temperature sensor has failed. The heater will not run until the fault is cleared or the control unit is repaired/replaced.

Most likely causes

Internal control unit (ECU) fault or end-of-line programming/checksum error common
Heater lock-out active after repeated faults (overheat, false start, etc.) common
Control unit miscoded for the wrong fuel type or set to neutral/disabled less common
Internal room-temperature sensor defective less common
Customer/W-bus communication line defective rare

Safe checks you can do yourself

Confirm the displayed code on a combination timer or count the long blink pulses on a rotary/Multi Control element (after five short signals, count the long flashes).
Verify the heater was specified for your fuel (diesel vs petrol/gasoline) matches the installed unit.
Inspect wiring/fuse and connector contacts for corrosion or looseness.

How to reset / clear F00

To clear an active heater lock-out: switch the heater on, then remove the heater's fuse.
Wait more than 2 seconds, reinsert the fuse, and switch the unit on again.
If the code persists, the control unit likely needs professional diagnosis or replacement.

When to call a technician

If the code returns after a single reset attempt, or if PC diagnostics show a control-unit/EOL/coding error, have a Webasto-trained technician handle it - a locked-out heater can only be returned to service after professional repair.

Applies to

Air Top EVO 40 · Air Top EVO 40 B (petrol) · Air Top EVO 40 D (diesel) · Air Top EVO 55 · Air Top 2000 STC

FAQ

What does Webasto Furnace code "F00" mean?

How do I reset Webasto Furnace F00?

To clear an active heater lock-out: switch the heater on, then remove the heater's fuse. Wait more than 2 seconds, reinsert the fuse, and switch the unit on again. If the code persists, the control unit likely needs professional diagnosis or replacement.

What is the most common cause of F00 on a Webasto Furnace?

The most likely cause is internal control unit (ecu) fault or end-of-line programming/checksum error.

Related · Webasto furnace

F01
No start - the heater attempted ignition and, even after a r… F02
Flame abort / flame failure - a flame was established but we… F03
Supply voltage out of range - the heater's operating voltage… F04
Premature flame detection - the flame/exhaust temperature mo… F07
Fuel pump fault - the dosing/fuel pump circuit shows an open… F08
Drive/combustion-air motor fault - the fan motor has an open…

Sources

Air Top Evo 40 / Air Top Evo 55 - Fault Codes / Troubleshooting (Fig. 503) — Section 5.4, Fault code F 00 (Butlertechnik / Webasto)
Webasto Air Top 2000 STC Fault Error Codes — Section 5.5, F00 (Butlertechnik / Webasto)

Note: On combination timers codes F01-F15 show numerically; F16-F19 appear as '--'. The 2000 STC numbers F00 as 'defective control unit' and outputs heater lock-out separately as F12/HEX 07.

● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.