Vaillant boiler showing F75
F75 means the pump ran but the boiler saw no pressure change. Common on ecoTEC models, usually an engineer job.
What it actually means
F75 appears when the pump starts but the boiler's pressure sensor does not detect the expected rise. Vaillant's electronics then stop the boiler as a precaution.
The usual suspects are a tired pump, a sticky pressure sensor, or air and sludge in the system confusing the reading.
Try this first, before you spend a penny
- 1
Check the pressure anyway
If the gauge is below 1 bar, top up to about 1.2 bar and reset. Low pressure can contribute.
- 2
Reset once
Press reset. If the boiler runs normally afterwards, keep an eye on it. If F75 keeps returning, stop resetting.
When it is a pro job
A recurring F75 needs an engineer with the right test kit to check the sensor and pump. Both are known wear items on this range and the fix is routine for someone who does it weekly.
Gas Safe registered heating engineer
Typical UK range covering a sensor clean or replacement up to a new pump. Parts availability for ecoTEC models is good, which keeps costs sane.
£150 to £400
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