An F23 error in Vaillant boilers indicates that a momentary blockage has occurred due to an excess of temperature in the equipment. The excess temperature was possibly due to a failure in the circulation pump, and therefore a lack of water. But as excessive temperature rises in a boiler can occur for various reasons, this means that the F23 error in Vaillant boilers is still a generic cause. Therefore, you have to analyze it in detail to find out which of the possible causes is specifically causing the blockage. Let’s look at the causes and solutions for this malfunction.
What does an F23 error mean in a Vaillant boiler
To analyze the F23 error in the Vaillant boiler, let’s take as a reference the manual of the ecoTEC Plus model, but it applies just as well to other models (for example, for the atmoTEC and turboTEC).
According to the manual, F23 error (or F.23) means that a safety shutdown has occurred due to excessive temperature variation. This can have several different causes: the pump may be blocked or have reduced power, air may be present inside the unit, or the inlet and return NTC may be interchanged.
How to fix an F23 error in a Vaillant boiler
When an F23 error appears in a Vaillant boiler, it means that during start-up the equipment has detected an excess of temperature due to a possible lack of water, which is almost certainly due to a water circulation failure linked to the water circulation pump being blocked or faulty.
Lack of water due to a blocked pump
The failure in the circulation pump is solved by unblocking it or replacing it with a new one. How to unblock the water circulation pump of your boiler? It’s a rather simple procedure. Open the cover of your boiler and locate the water circulation pump. Consult your instructions manual to find out what it looks like and where it is located. Once you have located the circulation pump, you can unblock it through these two methods:
- First method: Take care that the shaft of the water circulation pump has a plug with a very noticeable groove in it. Unscrew it with a wide-bladed screwdriver and pull it out. Inside you will find the shaft with a center in the shape of approximately a 4-pointed star. Use the same screwdriver or a large crosshead screwdriver, insert it into the star and try to turn the shaft. If that is the problem, you may find it a little stiff. Move it clockwise until it softens. It may be hard at first, but keep trying and you may be able to get it unstuck. Use a little force if necessary, but don’t use too much.
Lack of water due to a blocked pump
The failure in the circulation pump is solved by unblocking it or replacing it with a new one. How to unblock the water circulation pump of your boiler? It’s a rather simple procedure. Open the cover of your boiler and locate the water circulation pump. Consult your instructions manual to find out what it looks like and where it is located. Once you have located the circulation pump, you can unblock it through these two methods:
- First method: Take care that the shaft of the water circulation pump has a plug with a very noticeable groove in it. Unscrew it with a wide-bladed screwdriver and pull it out. Inside you will find the shaft with a center in the shape of approximately a 4-pointed star. Use the same screwdriver or a large crosshead screwdriver, insert it into the star and try to turn the shaft. If that is the problem, you may find it a little stiff. Move it clockwise until it softens. It may be hard at first, but keep trying and you may be able to get it unstuck. Use a little force if necessary, but don’t use too much.
In addition, the cold water inlet tap of the boiler may be faulty, and it might look like you are letting water in, but it’s not coming in at all, or it is not coming in in sufficient quantity, and that is why the boiler shows signs associated with lack of water. Make sure that this is not the case, and if necessary, replace the inlet faucet.
Something else you might want to think about is what causes the water supply. If after fixing the error it happens again at some point, perhaps the boiler has a water leak that will have to be repaired. It can be in several places, but it often appears somewhere in the heating system, in one of the radiators, or even through the boiler’s safety valve.
When dealing with this kind of error which might be due to several causes, one fault can easily be mistaken with another, until it’s almost impossible to figure out where the real problem lies. Our advice is to go to a qualified and experienced technician, so that he can determine which of the possible causes is triggering the error in your case.