Vaillant aroTHERM F.729 fault code

What it means

Compressor outlet temperature too low

Compressor-outlet temperature stayed below 0 °C for more than 10 minutes, or fell below −10 °C while in the operating envelope — usually liquid returning to the compressor (flooding).

UK models this code applies to

From the Vaillant service literature we hold (Vaillant hydraulic station installation & maintenance instructions 0020257319 (VWL 57…127/5 IS), fault-message table) — not a scraped list.

Now the harder half: proving what caused it

F.729 names a symptom, not a root cause. In the app, the same code opens a guided investigation: what to measure first, the expected values for your exact model, and an honest verdict — including “nothing in this machine is broken” when that's what the readings say.

Free, no sign-up. Pick the model and follow Vaillant aroTHERM's own chart for it, one question at a time.