FAQ
TL;DR: Audi A6 C6 parking heater issues often relate to the 4°C threshold; “It starts from 4 deg. down.” Use VAG diagnostics, check fuses, and fix pump/wiring faults before buying used units. This helps A6 3.0 TDI owners restore Webasto heat. [Elektroda, andrzej20001, post #17503239]
Why it matters: You avoid costly, unnecessary replacements by targeting the exact fault that blocks parking heat.
Quick Facts
- Auto-start threshold: the heater engages from 4°C down; above that it won’t auto-heat. [Elektroda, andrzej20001, post #17503239]
- Factory Webasto faults can be read via VAG; a fuse pull/battery disconnect can reset it. [Elektroda, marcin.koz2910, post #17502436]
- Prerequisites: fuel in the tank and correct battery terminal voltage, or it won’t switch on. [Elektroda, _Megamax_, post #17533041]
- Edge case seen: “short circuit in the positive lead from the circulation pump,” heater stayed off. [Elektroda, kilun1, post #17532875]
What outside temperature triggers the Audi A6 C6 Webasto to start?
Auto-heat engages at or below 4°C. Above that, it won’t start automatically. “It starts from 4 deg. down.” If heating still doesn’t run below 4°C, look for stored faults. Manual parking-heat may also be blocked by faults. [Elektroda, andrzej20001, post #17503239]
Does ambient temperature block manual Parking Heating on a full parking-heater setup?
If your car has a full parking heater, ambient temperature should not prevent manual activation. If it still refuses to start, treat it as a fault condition and scan the system. This differs from auxiliary-only heaters that follow ambient thresholds. [Elektroda, marcin.koz2910, post #17503221]
My MMI flips Parking Heating from ON back to OFF—what does that indicate?
That behavior shows the system refuses activation. The menu toggles back to OFF when the heater won’t engage. Users reported ON switching to OFF within seconds. Proceed to fault reading and basic power checks next. [Elektroda, kilun1, post #17502210]
Ventilation works but heating doesn’t—what should I check first?
Focus on the heating path. A failed coolant circulation pump can block the heater from starting completely. Even with ventilation working, the heater will not run without proper pump operation. Inspect pump power and wiring before replacing parts. [Elektroda, andrzej20001, post #17533115]
How do I diagnose the Webasto without wasting money on parts?
Start with a scan and a power reset.
- Connect VAG/VCDS and read faults for the factory Webasto module.
- Note codes and live data, then clear and recheck.
- Pull the Webasto fuse or briefly disconnect the battery to reset, then retest.
[Elektroda, marcin.koz2910, post #17502436]
Will disconnecting the battery clear Webasto faults?
A power cycle can reset the heater and clear transient lockouts. Pull the Webasto fuse or disconnect the battery briefly. This won’t fix a hard fault like a shorted pump. Always rescan after a reset to confirm persistent errors. [Elektroda, marcin.koz2910, post #17502436]
My scan shows “short circuit in the positive lead from the circulation pump”—what now?
Treat this as a wiring or pump failure. Inspect the pump connector, harness, and pump for damage. Repair wiring or replace the pump as needed. The heater will remain shut down until the short is resolved. Clear codes and retest afterward. [Elektroda, kilun1, post #17532875]
Do I need fuel and good battery voltage for the heater to switch on?
Yes. “For the parking heater to switch on, you need to have fuel in the tank and voltage on the battery terminals at the correct level.” Low voltage or fuel level blocks startup. Verify both before deeper troubleshooting. [Elektroda, Megamax, #17533041]
Will it start once the outside temperature drops below 5°C?
Not if there is an active fault. The reported car still would not heat even after temperatures dropped. Once the underlying issue is fixed, the 4°C auto-start logic can work. Temperature alone won’t overcome hardware errors. [Elektroda, kilun1, post #17532875]
The remote flashes green, then blinks red fast—what does that mean?
That pattern matches a no-contact or failed handshake with the vehicle. The user observed a brief green LED, then rapid red blinks. Recheck pairing, signal, and whether the heater is permitted to start. Then scan for faults. [Elektroda, kilun1, post #17502210]
Is it smarter to replace only the pump or the whole Webasto unit?
Avoid buying a used heater blindly. First, read the errors to pinpoint the failure. If the code points to the pump circuit, repair that component instead of swapping the entire unit. Diagnose, then replace targeted parts. [Elektroda, marcin.koz2910, post #17502436]
Will a defective circulation pump stop the Webasto from running?
Yes. A failed pump prevents the heater from starting or circulating coolant. As one expert put it: “Circulation pumps defective. It won’t move.” Fix the pump issue before expecting successful starts. [Elektroda, andrzej20001, post #17533115]
It was 6°C outside and still nothing—does that tell me anything?
At 6°C, auto-heating will not engage due to the threshold. If manual parking heat also fails, suspect a fault. Record that temperature point in your diagnosis notes. Repair the fault, then test again near or below 4°C. [Elektroda, kilun1, post #17502210]
Can a quick “tinker” or reset get it to fire at 4°C?
Sometimes. One user reported success after tinkering and reaching 4°C. However, that won’t overcome a real fault like a shorted pump. Use resets only after recording codes and planning repairs. [Elektroda, andrzej20001, post #17503757]
