Vaillant [F.322] fault codewhat it means and how to fix it

The ecoTEC plus CS/1-5 is the first Vaillant boiler whose pump reports on itself in detail, and F.322 is one of a family of pump codes — F.320 to F.330 — that no two-digit range has. Vaillant print it as "the heating pump has overheated; the temperature could not be lowered by the limp home mode", with the single cause "the pump temporarily reports excessive temperatures in the electronics" and the instruction to check the pump and replace it if required.

Two things in that wording are worth understanding. "Limp home mode" is the CS/1-5's name for running at reduced performance instead of stopping: when the pump first reports a high temperature the boiler eases off and carries on, and F.322 is what appears when easing off did not work. And it is the pump's electronics that are hot, not the water: modulating pumps carry their control electronics in the motor housing and those have a temperature limit of their own. A pump can run hot because it is failing, because it is working far harder than it should against a blocked or restricted circuit, or because the boiler compartment itself is hot.

Vaillant's table names only the pump, so this page keeps the surrounding causes clearly labelled as context rather than as their words. F.320 is the pump blocked, F.321 its electronics defective, F.323 dry running, F.324 its connection interrupted and F.325 a general pump fault; each has its own page or is covered on F.325.