F72 means your Vaillant is kind of broken, but can you fix it? Or an engineer?
The majority of boiler companies program fault codes into their boilers as a way of letting homeowners know that an issue is present.
These error codes come with an assigned figure (e.g. F24, F54, F72) designed to communicate the nature of the problem.
This is because the Vaillant boiler manual will tell you what any given fault code means and provide a list of possible fixes.
How you solve a given boiler issue would depend on the nature of the problem.
Not only that but some issues can be fixed DIY while others must be solved by a professional.
But what about the F72 fault code, in particular?
Let’s take a look!
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What Does F72 Mean?
Vaillant’s F72 error code generally means that you have an error with one of both of the NTC thermistors, namely, the flow and return NTC thermistors.
When this happens, the thermistors will provide faulty readings.
When the difference between the flow and return thermistors becomes too much and for too long, your boiler will shut off automatically and display the F72 fault code.
As is the case with other faults, the boiler shuts off for both practical and safety reasons.
Alternatively, an F72 could be triggered because the boiler ‘thinks’ that there is an issue with one or both of the NTC thermistors (more on that shortly).
You should also note that the NTC thermistors communicate with your boiler’s PCB.
This is relevant for the possible causes of the exact issue at hand.
Moreover, accurate NTC readings are needed for boilers to correctly regulate their water temperature.
So, as you can see, an F72 automatically shuts down your boiler for good reason.
A boiler, much like the human body, is a machine that requires components and parts to work as intended for a well-rounded balance and functioning system.
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What Causes an Incorrect Reading with an NTC Thermistor?
There are several likely reasons for an F72 fault:
Faulty Thermistor(s)
The primary reason for this is that one or both of your NTC thermistors are faulty.
It’s possible that the flow and/or return thermistors were faulty upon installation, or, if you have an old boiler, they more than likely deteriorated over the years.
Wiring Fault
It’s also possible that the issue lies with a wiring issue between your NTC thermistor(s) and the PCB.
Poor Installation
Upon installation, the installer may have fitted the flow and return thermistors with the incorrect pipes.
However, this is the least likely explanation since any competent installer would’ve tested everything out after installing your boiler.
Can I Fix an F72 Fault Myself?
Unfortunately, none of the issues that might explain an F72 can be solved DIY.
You must hire a Gas Safe Register engineer for legal and safety reasons.
Some Vaillant errors can (depending on the cause of said errors) be fixed by a DIYer but it really depends.
If there is a wiring fault, you’d need to hire an electrician whereas, generally, any other cause of an F54 error, could be solved by a heating engineer.
Is your Vaillant boiler experiencing some of the brand's most common fault codes? We have covered many Vaillant boiler error codes in the following guides:
Cost of Hiring a Heating Engineer to Fix an F54
The average labour cost of hiring a Gas Safe Register engineer in the UK is £30 to £60 per hour.
This excludes the cost of supplies and any waste removal expenses (if applicable).
The labour cost itself can also vary depending on factors like where you live. Here are some examples of hiring a heating engineer in notable UK cities:
London - £55 to £65 per hour.
Glasgow - £35 to £45 per hour.
Manchester - £35 to £45 per hour.
Birmingham - £85 to £95 per hour.
Liverpool - £85 to £95 per hour.
Cardiff - £30 to £40 per hour.
Belfast - £30 to £40 per hour.
Newcastle - £35 to £45 per hour.
Here are the overall costs of specific F72 fixes (i.e. labour + supply costs included):
Replace one thermistor - £40 to £160.
Replace two thermistors - £50 to £190.
Fixing a wiring fault - £30 to £150 *
Correcting a poor installation - £30 to £120.
Replace an entire boiler - £800 to £2,800.
*You’d need to hire an electrician to solve this issue.
You may be interested in Gas Engineer Allen Hart explaining the most common boiler problems and how you can resolve them in the video below:
We’ve included ‘replace an entire boiler’ for a reason. If your boiler has a host of issues causing an F72 fault and it is particularly old, it may be best to have it replaced.
Of course, for many homeowners right now, replacing their boiler may seem inconceivable given that it will probably cost around one to two grand.
However, you’ll be glad to know that it’s possible to purchase a boiler on finance! In other words, you can buy now and pay later. Sometimes, it’s even possible to do so with 0% interest.
Contact us if you have any questions about an F72 fault or a related issue with your Vaillant boiler.
Will my Warranty Cover Repairs or Replacement Work for an F72 Fault?
Your warranty may or may not cover an F72 fault repair.
However, it primarily depends on whether a manufacturing error resulted in the fault.
Not only that but even if you can show that a manufacturing error is at play, you need to confirm the following:
Your Vaillant warranty is still active.
You meet the terms and conditions that cover your warranty.
For instance, any domestic Vaillant boiler warranty requires that:
A Gas Safe Register engineer services your boiler annually.
A Gas Safe Register engineer installed and commissioned your boiler within six months of being despatched.
As you see, it’s not likely that your warranty will cover an F54 error.
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