Last updated on October 15th, 2024
The Vaillant F83 fault code, and all Vaillant fault codes, show on the display when there is a problem and your boiler locks out. Vaillant uses them to show you what might be wrong with the boiler not firing up.
I have been a full-time boiler repairer for over a decade and having fault codes on the screen when I arrive is very welcome. In this post, I’ll go through some of the reasons for your F83 fault and some potential fixes.
What Does F83 Mean?
The cause of an F83 fault is the boiler has been locked out due to dry fire. It could also mean that a part on the boiler is broken and needs to be replaced.
Here is what the Vaillant Ecotec manual says about their F.83 fault code:
How to Fix an F83 Fault
To fix the F83 fault, the first things I would do is:
- Bleed any air out of the heating system
- Make sure the pressure is around 1.5 bar and reset the boiler
- Check wiring on and test thermistors
- Check the gas rate and inlet pressure at the gas valve
Other Causes of an F83 Fault
Low boiler pressure is the most common cause of an F83 fault code, but here are some other potential causes:
- NTC thermistor is faulty: The flow or return temperature sensor can be out of calibration or not connected properly. This will need to be secured or replaced
- Thermistor wiring damaged or loose: The wiring on the thermistors will need fully checked from the thermistor to the PCB for any damage or loose connections. Any problems will need fixing or replaced
- Low heat input on heat exchanger: This can be caused by a gas valve problem or lack of thermal transfer from the combustion chamber.
Vaillant Fault Reset
The first thing I would do on a boiler that is not working, no matter what fault code is showing, is to check the pressure and reset the boiler.
Knowing how to reset a boiler is the simplest way to get it working again, as it might have just locked out. To reset a Vaillant boiler, you must find the reset button. This is usually a flame with a line through it.
You have to press the button to reset it. Sometimes you have to hold it down for 3 seconds, but on some Vaillant boilers, it just needs to be pressed.
Vaillant boiler guides
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- Vaillant boiler leaking
- Vaillant F54 fault
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- Vaillant F75 fault
- Vaillant F28 fault
- Vaillant F29 fault
Summary
A Vaillant F83 error on your boiler can sometimes be easily fixed without opening the boiler. You should repressurise the boiler and reset it as your first port of call.
Feel free to ask any questions in the comments below, and I’ll do my best to help. If you found this post helpful, please consider sharing it.
Dear Sir i have a Vaillant comby boiler etec plus 937 two days ago the hot water to the bath and sink upstairs slowed down to a trickle ,but the kitchen hot water was as normal , i had a plumber to look at it and he said the hot water pipe must be blocked up ,it can not ber the boiler because the kitchen tap is has normal fast rate. so today i disconected the hot pipe upstairs under the sink and connected the cold water pipe to the hot pipe and disconected the hot pipe downstairs and put a hose pipe to the outside and tuned the cold water on and that proved that tha hot water pipe was not blocked up , please help ,regards terry ,email [email protected]