Heatline boiler repair across London
We repair Heatline boilers still in use. Ring us, day or night.
- Heatline Capriz, Monza and Vizo repaired
- All our engineers are Gas Safe registered
Makes we repair
How does booking a Heatline repair work, and what does it cost?
Booking: ring us any time, day or night, or send your details and we ring you back. We'll ask what the boiler is doing, and its model and any code on the display if you can see them. You don't need to know what's wrong. Finding the fault is the engineer's job. Then we tell you when an engineer can come, anywhere in Greater London.
What it costs: a repair's price depends on the part it needs, how long the job takes and when it's done. Our rates are higher in the evening, overnight and at weekends. Once the engineer has found the fault, the rate for the repair is agreed in writing before any work starts.
What happens on a Heatline repair visit?
A repair visit has three stages.
1. Before anything is touched
The engineer covers the floor around the boiler and asks what you have seen and heard since you rang.
2. Finding the fault
The engineer tells you which part has failed, whether they have it with them or must order it, and how long the work should take. No work is done until you say yes.
3. The repair
The engineer fits the part and checks the boiler runs as it should before leaving. The repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
What goes wrong on Heatline boilers most often?
Low pressure, failed lighting and a frozen condensate pipe are the problems Heatline's own manuals cover most:
- Low pressure. The code is F.22 on a Capriz 2, F22 on a CaprizPlus or Monza and F0 on the one-figure ranges. A Capriz 25 shows a red light. Heatline's guide asks owners to look at the gauge once a month, and a pressure that drops often needs an engineer.
- Not lighting. F.28 or F28 means the boiler tried to light and locked out. Heatline allows three resets before an engineer is needed.
- A frozen or blocked condensate pipe. In a frost, ice in the pipe outside shuts the boiler down. On a Sargon or Vizo Plus, a blocked condensate trap shows as F4.
- Pressure too high. Heatline's manuals bring it down by bleeding a radiator, never at the safety valve.
- No heating or hot water, and no code. Heatline's guide lists the simple causes: the power, the gas or water supply turned off, the settings, the pressure or the controls. We'll ask about each when you ring.
- Frost. Heatline asks for the heating to stay on in freezing weather, as the boiler's frost protection doesn't cover the water pipes.
Whichever it is, we'll ask what the boiler is doing when you ring.
Sources: Heatline's operating instructions for the Capriz 2, and its installation and servicing manuals for the CaprizPlus, the Capriz 25, the Solaris, the Sargon and the Vizo Plus.
Worth knowing
Heatline boilers are no longer made, and we still repair them. The Vaillant Group, whose brand Heatline was, no longer lists it among its brands. Heatline's own website closed between September 2025 and October 2026.
Heatline fault codes and what they mean
Heatline fault codes take three forms, by the boiler's age:
- F.28, with a dot, on a Capriz 2
- F28, without a dot, on a CaprizPlus or Monza, with the same meaning
- F and one figure on a Solaris, Sargon or Vizo Plus, where the numbers mean other things
The codes below are from Heatline's manual for the CaprizPlus and Monza, in its order. The Capriz 2's guide covers F.22 and F.28, with the same meanings. Heatline's rule is three resets at most, and a code that keeps coming back needs an engineer.
Heatline was a Vaillant Group brand, and its codes follow the group's numbering. The CaprizPlus and Monza use the same numbers, with the same meanings, as Glow-worm boilers of the same years. The Capriz 2's F.22 and F.28 mean what they do on a Vaillant or Glow-worm today. Glow-worm boilers: their codes and repairs. Vaillant boilers: their codes and repairs.
F28Heatline F28 (F.28): the boiler tried to light and failed
What it means: The boiler tried to light, failed and locked out. A Capriz 2 locks out after three tries in a row, and a CaprizPlus after retrying by itself several times.
Possible causes, as the manual lists them:
- no gas reaching the boiler, or too little
- the gas valve set wrongly
- the ignition and flame-sensing electrode or the igniter
What you can do: press reset, and the boiler tries again. Heatline allows three resets. If F28 comes back after the third, ring us.
On a Solaris, Sargon or Vizo Plus, a failed lighting shows as F4. On a Sargon or Vizo Plus, F4 also covers a blocked condensate trap.
F29Heatline F29: the flame went out while running
What it means: The burner lit, then lost its flame while the boiler was running.
Possible causes, as the manual lists them:
- too little gas or none
- the gas valve's setting
- the electrode or the igniter
The causes are the same as for F28.
What you can do: nothing at home. Heatline's guides give no step for F29, so it needs an engineer.
F22Heatline F22 (F.22): the water pressure is too low
What it means: The water pressure in the heating is too low for the boiler to run.
Possible causes, as the manual lists them:
- a return valve shut
- the pump disconnected
- a leak in the system
What you can do: on a Capriz 2, Heatline's guide shows how to top up:
- Open all the radiator valves.
- Open the filling cock slowly, as the installer showed you, until the display reads 1 to 1.5 bar.
- Close the filling cock.
If F22 comes back, ring us. The manual lists a leak among its causes, and Heatline's guide sends a pressure that drops often to an engineer.
F20Heatline F20: the boiler has overheated
What it means: The overheat safety device has tripped and shut the boiler down.
Possible causes, as the manual lists them:
- the pump not working
- the wiring
- the flow and return isolating valves left shut
What you can do: nothing at home. Heatline's guides send F20 to an engineer.
On a Solaris, Sargon or Vizo Plus, overheating shows as F1. On a Sargon, a blown thermal fuse stops any reset until it is replaced.
F32Heatline F32: the fan or the air pressure
What it means: The air pressure is wrong, because the fan isn't reaching its proper speed.
Possible causes, as the manual lists them:
- the fan's speed
- the flue from end to end
- the fan's wiring
What you can do: nothing at home. Heatline's guide says never to alter the flue, so ring us.
On a Solaris, Sargon or Vizo Plus, a fan fault shows as F8 or F9, or F7 on a Solaris.
F00/F01/F10/F11Heatline F00, F01, F10 and F11: a temperature sensor
What it means: A flow or return temperature sensor can't be read. F00 and F01 mean a break in the circuit, at the flow and at the return sensor. F10 and F11 mean a short circuit.
Possible causes, as the manual lists them:
- the sensor's plug and connections
- the wiring loom
- the sensor itself
What you can do: nothing at home.
F71, F72, F84 and F85, in the list, are the same sensors misreading or fitted wrongly. On a Solaris, Sargon or Vizo Plus, a sensor fault shows as F2, F3, F5 or F6.
MoreEvery other Heatline code, in one list
Every other code in Heatline's manual for the CaprizPlus and Monza. The Capriz 2's guide names two codes, F.22 and F.28, and sends any other to an engineer. We'll ask for the code when you ring.
F23The flow and return are too far apart in temperature
Possible causes
Water not circulating properly: the sensors' connections or the pump's speed
F24The temperature is rising too fast
Possible causes
The pump not working properly, or the flow and return valves shut
F26The gas valve's motor has a fault
Possible causes
Its cables loose or faulty, or the gas valve
F27A flame is sensed when there should be none
Possible causes
The manual's table groups its checks with F26's and doesn't separate them
F49A fault on the link to the controls
Possible causes
A short on the controls' wiring, or controls fitted or wired wrongly
F61 to F65, F67A main board fault: the gas valve's control or closing, the memory, a sensor reading that swings, the board too hot, or the flame signal
Possible causes
The main board or its connections, or the boiler's product code
F68The flame signal is unstable
Possible causes
Too little gas, the gas valve's setting, the electrode or the igniter
F70The control panel doesn't match the main board
Possible causes
The wrong product code set, or the wrong board fitted
F71The flow sensor's reading is stuck
Possible causes
The sensor unclipped from its pipe, or faulty
F72The flow and return sensors always disagree
Possible causes
A sensor's connections, or a faulty sensor
F73The heating pressure sensor is shorted or disconnected
Possible causes
Its wiring or connections
F74The heating pressure sensor is faulty
Possible causes
The sensor
F76The heat exchanger's thermal fuse has a fault
Possible causes
The fuse's connections. For the fuse itself, the manual's remedy is a new heat exchanger.
F77A fault found at the gas valve or a condensate pump
Possible causes
A faulty gas valve, or the condensate pump where one is fitted
F83No water, shown by the temperature not rising when the burner lights
Possible causes
A return valve shut, the pump disconnected, or a leak
F84The flow and return readings don't make sense
Possible causes
The two sensors swapped or disconnected
F85The flow and return sensors are fitted wrongly
Possible causes
Both sensors on the same pipe
F86The underfloor heating contact is open
Possible causes
The contact open, or its sensor disconnected or faulty
ErrThe control panel has a fault
Possible causes
The lead from the control panel to the main board, or the panel
Solaris, Sargon and Vizo Plus: the one-figure codes, and the Capriz 25's lights
The one-figure list comes from Heatline's manuals for the Solaris and the Sargon. The Vizo Plus manual lists the same faults in the same order. The one-figure numbers don't match the CaprizPlus's two-figure codes, and in this list F1 is overheating.
F0The water pressure is too low or too high
Possible causes
The heating's water pressure
F1Locked out from overheating
Possible causes
The overheat thermostat or, on a Sargon or Vizo Plus, the thermal fuse. A blown fuse stops any reset until it is replaced.
F2The hot water temperature sensor is damaged
Possible causes
The hot water sensor
F3The main temperature sensor is damaged
Possible causes
The main (primary) sensor
F4Locked out after failing to light
Possible causes
The ignition. On a Sargon or Vizo Plus, a blocked condensate trap as well.
F5The flue gas temperature sensor is damaged
Possible causes
The flue sensor
F6The outside temperature sensor is damaged
Possible causes
The outside sensor
F7 (Solaris)A fault in the fan's feedback signal
Possible causes
The fan or its signal
F8The fan's speed is outside its range
Possible causes
The fan
F9The fan is turning when it should be still
Possible causes
The fan or its control
OC, CCAn outside sensor connected, with weather compensation on, or disconnected, with it off
Possible causes
A message, not a fault
Capriz 25, 28, 25S and 28S: the lights. A green light means the power is on, and the red lights in a row show the water's temperature. A red light flashing in its own place names one of these faults:
- the heating sensor
- the outside sensor
- the air pressure switch
- the flame or gas
- low pressure
- the overheat thermostat
The whole bar flashing means the hot water sensor. The flame light and the overheat light, first and second from the right, are the two a reset clears, on a Vizo as well.
Other makes number their codes their own way. The codes on every other make, and what each kind means.
Sources, read on 9 October 2026: Heatline's installation and servicing manuals for the CaprizPlus (0020112883-03, June 2011) and the Monza (0020112884-03, June 2011), and its Capriz 2 operating instructions (0020206382_02, August 2015), from the Internet Archive's copies of Heatline's own website.
Which Heatline boiler do you have, and how does it show a fault?
Heatline boilers are no longer sold, and we repair every Heatline range still in London homes. Heatline, a Vaillant Group brand, made boilers that show a fault as an F code or as flashing lights, depending on their age. The same number can mean something else on an older one. We'll ask for the model and the code when you ring.
Not every message is a fault:
- On a CaprizPlus or Monza, an S. code shows what the boiler is doing, such as lighting or waiting.
- On a Capriz 2, OFF means standby, and a flashing pressure figure means the pressure is out of range.
- When the power comes on with the pressure low, a CaprizPlus vents air for 5 minutes and doesn't light in that time.
- On a Solaris or Sargon, OC and CC are messages about an outside sensor.
We'll ask what the display shows.
How do you reset a Heatline boiler?
Heatline boilers reset in one of four ways, by range, as Heatline's guides show:
- Capriz 2: press the reset button, and the boiler tries to light again.
- CaprizPlus and Monza: press reset.
- Capriz 25, 28 and Vizo: turn the function switch to stand-by, give it 30 seconds, then turn it back.
- Solaris and Sargon: switch to stand-by, give it 30 seconds, then switch back on. On a Sargon, a blown thermal fuse, F1, won't reset.
The Capriz 2 and CaprizPlus manuals allow 3 resets at most. If the code comes back after that, ring us.
The pressure: with the system cold, a Capriz 2 should read 1 to 1.5 bar. Heatline asks owners to look at its gauge once a month. A Capriz 25, Vizo or Solaris should read 1 to 2 bar, topped up to 1.5.
The Capriz 2's guide shows how to top up at the filling cock, and the older guides at the filling loop. If the pressure is too high, bleed a radiator to bring it down. Heatline's manual says to use a radiator's valve, never the safety valve. If the pressure keeps dropping, ring us.
In a frost, ice in the condensate pipe outside shuts a Heatline down. Where the frozen pipe is at ground level:
- Thaw it with warm, never boiling, water.
- Reset the boiler.
In freezing weather, Heatline asks for the heating to be left running. When a boiler won't fire up, and frozen condensate pipes.
Sources: Heatline's operating instructions for the Capriz 2, and its manuals for the CaprizPlus, the Capriz 25, the Vizo, the Solaris and the Sargon.
Is your Heatline boiler still under guarantee?
Heatline gave the Capriz 2, its last range, a 2-year guarantee on parts and labour. Heatline's terms for the CaprizPlus and Monza asked for the boiler to be registered within 30 days of fitting, with its Benchmark checklist filled in. The terms also asked for any repair under the guarantee to be done by an engineer Heatline approved, with its say-so first.
Most Heatline boilers are now past their guarantee, but a Capriz 2 fitted in the last two years may still be inside its 2 years. Its serial number's third and fourth digits give the year it was made.
Heatline's own website has closed. For guarantee help, the Capriz 2's guide sends owners to Heatline's address in Belper, Derbyshire. That is the address of Vaillant Group UK, the company behind the brand.
A boiler still under guarantee is usually repaired at no charge by whoever its guarantee papers name, so look at those first. Once the guarantee has ended, or for a fault it doesn't cover, ring us. We are an independent firm, with no connection with Heatline.
Sources: Heatline's Capriz 2 page and brochure, its CaprizPlus guarantee terms and its Capriz 2 operating instructions, from the Internet Archive's copies of Heatline's website, and Companies House's record of Vaillant Group UK.
What does a Heatline boiler service cover?
Heatline's manuals ask for the Capriz 2 to be inspected every year, and maintained every two years, by a competent person. The manuals say once a year is usually enough for the CaprizPlus and Monza. The Solaris needs a service at least once a year.
The CaprizPlus manual's yearly list covers:
- the sensors
- the fan and the flame signal
- the thermal fuse
- the pressure sensor
- the expansion vessel's charge
- the combustion and gas rate
- leaks
- the flue
- electrical safety
- cleaning the condensate trap
The checks are recorded in the Benchmark service record.
We service every Heatline model, and give you the rate on the call. What a boiler service includes, check by check.
15% off a new boiler, fitted
The 15% comes off the price of a new boiler installation. We quote from photos of your old boiler, or after a free survey visit. Now is the time to replace an old or discontinued boiler.
Terms: 15% off everything in the price we quote for a new boiler installation. That means the boiler, its flue and controls, and the fitting. The offer is for installations booked by 31 December 2026. One offer per home, and not with any other offer.
Do you cover my part of London?
Yes: we travel all over Greater London, day and night, to repair Heatline boilers in every borough, north and south of the Thames. Pick your side of the river to see the areas.
North of the river
Every borough north of the Thames: Barnet and Enfield at the top, Hillingdon in the west, Havering in the east, and central London in between.
South of the river
Every borough south of the Thames: Richmond and Kingston in the west, Bexley in the east, and down through Croydon to Sutton and Bromley.
The other makes we repair
Every main make, combi, system and regular. Pick yours for its common faults, its codes and how we repair it.
Questions about Heatline boilers
Do I need to know what's wrong with my Heatline boiler before I ring?
No. Ring and say what the boiler is doing, or what you can see or hear, and we'll ask the rest. Finding the fault is the engineer's job.
Do you charge more in the evening or at weekends?
Yes. Our rates are higher in the evening, overnight and at weekends.
Can you repair an older Heatline boiler?
Usually, yes. It depends on the boiler's condition and whether its parts are still made. We'll ask for the model when you ring.
Is my Heatline boiler worth repairing?
Often, yes. Age alone doesn't decide it. What decides it is the rate for the repair against a new boiler, and how often the boiler has failed. The engineer gives you the rate for the repair, and the choice is yours. When a new boiler makes more sense.
Will a repair affect my Heatline guarantee?
While the guarantee runs, look at its papers first. They say who repairs the boiler under guarantee, and who may work on it. Once it has ended, any Gas Safe registered engineer can repair it.
Do you fit Heatline's own parts?
Yes, the maker's own parts wherever they are available. Each repair is guaranteed for 12 months, covering the parts we fit, the labour and any return visit.
How much does a Heatline boiler repair cost?
The cost of a repair depends on the part, how long the job takes and when it's done. The rate is agreed in writing before the repair starts. How our rates work.
Is Heatline still made?
Heatline boilers are no longer made. The Capriz 2 was the brand's last range, and Heatline's website has since closed. We still repair every Heatline, from the Capriz 2 back to the Solaris and Sargon, and we'll ask for the model when you ring.
What does F28 mean on a Heatline boiler?
F28, or F.28 on a Capriz 2, means the boiler tried to light, failed and locked out. Heatline allows three resets. If the code comes back after the third, ring us. On a Solaris, Sargon or Vizo Plus, the same fault shows as F4.
Why does my Heatline boiler keep losing pressure?
Pressure that keeps falling on a Heatline boiler points to a leak. The CaprizPlus manual lists a leak in the system among the causes of F22. The Capriz 2's guide sends a pressure that drops often to an engineer. Top up to 1 to 1.5 bar as the guide shows, and ring us.
How can I tell how old my Heatline Capriz 2 is?
A Capriz 2's serial number gives its age, as Heatline's guide explains. The third and fourth digits are the year it was made, and the fifth and sixth the week. A Capriz 2 fitted in the last two years may still be under its 2-year guarantee.
Who makes Heatline boilers?
Heatline is a trademark of the Vaillant Group. The company behind it is Vaillant Group UK, of Belper in Derbyshire. It was called Hepworth Heating from 1991 to 2005, and Glow-Worm before that. Glow-worm and Vaillant are Heatline's sister brands. Vaillant boilers: their codes and repairs.
Don't know what has failed? You don't have to.Ring and say what you can see or hear. Finding the fault is our job.
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A real person answers and gives you the rate on the call. No work starts until you say yes, and repairs are guaranteed for 12 months: parts, labour and any return visit.
