Makes we repair
What does F83 mean?
F83 means the burner lit, but the boiler's temperature sensors saw little or no rise in the water's temperature. A Vaillant or Glow-worm boiler looks for that rise as the burner starts. When the flow or return sensor sees too little change, or too slow a change, the boiler stops and shows F83. Several of the makers' manuals call it dry fire, and too little water in the boiler is the first cause they name.
An F83 can come from something as simple as low pressure. Other causes are a temperature sensor not sitting against its pipe, the sensor's wiring, and water not moving round the heating. You can read the pressure gauge yourself, and on a Glow-worm Energy you can reset the boiler. The rest is an engineer's job.
Which boilers show F83?
Vaillant and Glow-worm belong to the same group, and both show F83. On either make, F83 means the water didn't warm as it should when the burner started. The way the manuals word it depends on the boiler's age. Every boiler fault code, make by make.
Vaillant F83
Vaillant's ecoTEC plus models before 2023 and the ecoTEC pro show F.83. Their manuals word it as too little difference between the flow and return temperatures.
The ecoTEC exclusive, the ecoFIT pure and the open-vent ecoTEC plus show F.83 too. On these boilers, F.83 means the sensors see little or no change in temperature as the burner starts. The ecoFIT pure's and open vent's manuals call it dry fire.
The ecoTEC plus range from 2023 shows F.083, with a line of text. That range's manual gives F.083 for no rise in temperature, or too slow a rise, as the burner starts.
On the ecoTEC of 2004 to 2006 and the turboMAX plus, the code their manuals call dry fire is F.22. Vaillant boiler repair, and every other Vaillant code.
Glow-worm F83
Glow-worm's Energy, Betacom4 and Easicom3 show F.83, which their manuals call dry fire. As the burner starts, the flow or return sensor sees little or no change in temperature.
The Compact and MicraCom show F.83 for a temperature that swings. The causes are the same, with low pressure first.
The Betacom2, Betacom a and Ultracom2 write it F83, without a dot. Their manuals put it down to no water in the heating, so the temperature doesn't rise when the burner lights.
Glow-worm's fault-code tables for the Flexicom cx and the first Ultracom have no F83. On those boilers, F22 covers low pressure or the water warming too slowly as the boiler lights, so read the model before the code. Glow-worm boiler repair, and every other Glow-worm code.
What causes F83?
F83 has four groups of causes. Vaillant's manual for the current ecoTEC plus lists them in this order, for the engineer to work through:
- The pressure. The system pressure too low.
- The flow sensor. The sensor not lying against the flow pipe, or its wiring.
- The return sensor. The sensor not lying against the return pipe, or its wiring.
- The water. Too little or no water in the boiler. The engineer fills the system and looks for leaks.
Glow-worm's manuals name the same causes, too little water and a sensor not sitting on its pipe. The Compact and MicraCom manuals put low pressure first. Vaillant's and Glow-worm's own fault-code pages add a circulation fault, from the pump, a valve or a blockage. The manuals for the older Betacom2 and Betacom a name a closed return valve, the pump disconnected and a leak in the heating.
No maker ranks these causes by how often each one happens, so the list keeps Vaillant's order. Boiler repair across London, sensors and pumps included.
F75 is the makers' code for the pressure barely rising as the pump starts, another fault in the same water circuit. The F75 fault code page, for a pressure that barely rises as the pump starts.
Sources: Vaillant's installation and maintenance instructions for the current ecoTEC plus, Glow-worm's for the Energy7, the Compact and the MicraCom, the Betacom2 and Betacom a manuals, and both makers' fault-code pages.
Worth knowing
Low pressure comes first among F83's causes in Vaillant's manual for the current ecoTEC plus. Reading the pressure gauge is a check you can make yourself.
What can you safely check?
F83 leaves you two safe checks. The first is the pressure gauge, which the makers' user guides show you how to read and top up. The second is the reset a Glow-worm Energy's guide gives. Never take off the boiler's case, and never touch anything that carries gas.
1. What does the gauge read?
The pressure shows on the boiler's display, or on a needle gauge on older boilers. Read it with the heating off and the boiler cool. If it reads low for your boiler, top it up with the filling loop, as your user guide shows. The F22 fault code page, for each maker's pressure levels and topping up step by step.
2. A Glow-worm Energy: reset it
A Glow-worm Energy combi's or system boiler's user guide gives a reset for F.83. Press the reset button. If F.83 shows again after a second press, the boiler waits 45 minutes, showing S.54, then tries again.
Vaillant's user guides give no reset for F.83 and send it to a competent person, so on a Vaillant, ring us.
3. Still showing F83?
A boiler that still shows F83 with the pressure right needs an engineer. The checks left are all inside the case:
- the sensors on the flow and return pipes
- the sensors' wiring
- the pump
- the water inside the boiler
A system you keep topping up is losing water, and where it goes needs finding too. Ring us and read out the code.
Sources: the user guides for the Vaillant ecoTEC plus and the Glow-worm Energy7, and both makers' fault-code pages.
When should you stop and ring an engineer?
F83 needs an engineer once the pressure is right and the code is still showing. Any of these signs also calls for one straight away:
- The gauge reads within your user guide's range, yet F83 shows.
- On a Glow-worm Energy, F83 is back after the 45-minute wait.
- The pressure keeps dropping, so you keep topping up.
- Water shows where it shouldn't, with drips or damp patches under the boiler, a radiator or a valve.
- Going further would mean taking the boiler's case off.
Vaillant's and Glow-worm's own fault-code pages send F83 to a heating installer first. The fault can come from the way the boiler works with the heating system. If you smell gas, leave the boiler alone and open the gold "Smell gas?" bar on this page for the free emergency number. Otherwise, ring us, as finding why the water isn't warming is work for our Gas Safe registered engineers.
The question we'll ask when you ring about F83
When you ring about F83, we'll ask first what the pressure gauge reads, and whether the system has needed topping up before. The answers split the causes in two:
- Low pressure, or a system losing water, points to the water.
- F83 with the pressure right points to a sensor, its wiring or the water not moving round.
We'll also ask for the model, as printed on the boiler, and the exact code on the display.
What changes the price of the fix?
The cost of putting an F83 right depends on its cause. Bringing the system back to pressure may need no part at all. A sensor refitted or replaced, a pump, or a leak to find and mend is more work. The rate is agreed with you on the call, before an engineer sets off, and no work is done until you say yes. How our rates work.
Do you cover my part of London?
Yes: we fix F83 faults all over Greater London, day and night, 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.
Questions about F83
Can I keep resetting the boiler?
A reset for F83 is a step one maker's guide gives. On a Glow-worm Energy, press reset, and after a second press the boiler waits 45 minutes before it tries again. Vaillant's user guides send F83 to a competent person. If F83 comes back, the cause is still there and resetting again won't fix it, so ring us.
Is F83 dangerous?
F83 itself is a safety stop. The boiler shuts down when the burner lights and the water doesn't warm as it should. None of F83's causes in the makers' manuals lies in the gas. A smell of gas is still an emergency, though. Open the gold "Smell gas?" bar on this page for the free number.
Why has F83 come back?
An F83 that returns after a top-up or a reset means its cause is still there. Any of these can bring it back:
- a system still short of water, or losing it
- a sensor that isn't sitting against its pipe
- water not moving round the heating, which Vaillant's and Glow-worm's pages put down to the pump, a valve or a blockage
An engineer goes through each cause in turn.
How much does it cost to fix F83?
The price of an F83 repair comes down to its cause, and any part it needs. You'll know the rate before anyone comes out, as it is agreed on the call. How our rates work.
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.
Calls answered 24 hours a day
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.
