Vaillant Boiler Repair

• Burner: where the gas is lit. It heats the water passing through the boiler.
• Heat exchanger: a metal block the flame heats and the water runs through. Scale and sludge clog it over time.
• Fan: pushes the exhaust gases out through the flue. If it fails the boiler won't fire, for safety.
• Pump: pushes hot water round the radiators and back. A failed pump means the boiler heats up and then cuts out.
• Diverter valve: on a Vaillant combi, the motorised valve that switches between heating and hot water.
• PCB: the circuit board. The boiler's brain. It reads the sensors and decides what to switch on.
• Expansion vessel: a small pressurised tank that absorbs the water expanding as it heats. When it fails the pressure keeps climbing and dropping.
• Pressure gauge: shows the water pressure in the system. It should sit between 1 and 1.5 bar when cold.
• Flue: the pipe that takes the exhaust gases outside.
• Condensate pipe: the small plastic pipe that drains the acidic water a modern boiler produces. It freezes in cold snaps and stops the boiler.

• F22 low water pressure: the gauge reads under 1 bar and the boiler locks out. Usually a slow leak or the expansion vessel. Topping up takes a minute; finding the leak or replacing the vessel is an hour or two.
• No hot water but heating works: almost always the diverter valve on an ecoTEC combi. It sticks on the heating side. Replacing it is about an hour with a genuine part from the van.
• F75 pump or sensor fault: the pump, a blocked heat exchanger, or a sensor. Diagnosis first, then usually a one visit repair.
• F28 and F29 ignition lockout: the gas valve, the ignition electrode, or in winter a frozen condensate pipe. Thawing the pipe is ten minutes; a gas valve or electrode is a fixed price repair, usually same day.
• Pressure keeps rising then dropping: the expansion vessel has lost its air charge. Recharging it is quick; replacing it is a longer job.

• A new boiler for a valve or a sensor: if your Vaillant is under ten years old and the fault is a diverter valve, a fan or a sensor, repair it. Replacing a Vaillant to fix a small part is the most common piece of bad advice in this trade.
• A full powerflush on every repair: only needed when the system is genuinely sludged up, which shows as radiators cold at the bottom and a struggling pump. A single blocked radiator doesn't need the whole system flushed.
• Replacing the PCB on a guess: boards are expensive. A good engineer confirms the board is at fault before fitting one, because a board fault often turns out to be a sensor or a wiring problem.
• Worth paying for: a magnetic filter if you don't have one. It catches the sludge before it reaches the boiler and is the cheapest insurance a heating system can have.

Check the pressure gauge and, in winter, whether the condensate pipe outside has frozen. If the pressure is low, top it up and see if your Vaillant resets. If it's showing an error code you don't recognise, if it's leaking, or if it smells of gas, switch it off and message me. Most Vaillant boiler repairs in Walsall are fixed on the first visit. Contact me now