Vaillant F.75 fault – Water Pressure Sensor or Pump failure
The Vaillant F.75 fault code showing on the ecoTEC Plus or ecoTEC Pro boiler display, indicates that no pressure rise is being detected by the boiler’s Water Pressure Sensor, when the integral Pump initially starts up into normal running mode.
The displayed F.75 fault code is usually a result of one (of two) integral boiler components becoming defective.
- Firstly, it is possible that the ecoTEC boiler’s Pump has failed or is intermittently seizing up.
- Secondly (and much more likely), is that the boiler’s Water Pressure Sensor is partially blocked and is not detecting the correct pressure increase from the Pump on startup.
As indicated above, the usual cause of the F.75 failure, 80% of the time, is the Water Pressure Sensor not detecting any pressure increase from the Pump.
This is mainly due to the Sensor becoming blocked up by debris and dirty contaminated system water turning into a form of semi-solid sludge, over time.
The same dirty water, of course, will more than likely be circulating around many other parts in the central heating system.
Glowcare are Vaillant Approved Specialists, covering the Greater Manchester, Cheshire, Liverpool and Lancashire areas.
Many of our customers have experienced their Vaillant ecoTEC boilers playing up with intermittent F.75 issues, due to Water Pressure Sensor failures over the years.
Surprisingly, some of these boilers manage to limp on for a while, intermittently cutting out but not failing completely.
This seems to have been happening because the customers were putting the system pressure up a bit higher, on the boiler’s digital display or pressure gauge.
This action, of course, must not exceed the manufacturer’s specified pressure limits and parameters.
We at Glowcare do not recommend increasing the water pressure in the boiler to get around this problem, and advise that the defective Water Pressure Sensor is replaced as soon as possible.
So this slight pressure increase, sometimes kept boilers from completely failing. But obviously there is a limit to how much customers will want to put up with this, before addressing the Water Pressure Sensor issue, by having it replaced by a competent person, e.g. a Vaillant Specialist or a local Gas Safe Engineer.
Taking a look at what the manufacturer says in the Vaillant manual for the F.75 error fault code on the ecoTEC Plus or Pro boiler
Vaillant ecoTEC F.75 Fault Error Code – Plus and Pro Boiler
F.75 Fault Code
Pressure change not detected on Pump starting up.
Causes can be;
Water Pressure Sensor defective
Automatic Air Vent defective
Air within heating system
Not enough water in appliance
Possible by-pass adjustment
Expansion Vessel (external) connected to the return.
As has been said previously, it is usually one of two failed components that will be responsible for causing the F.75 fault error code.
- In rare instances, the expensive integral boiler Pump.
- More likely, the boiler’s Water Pressure Sensor.
A hint as to which one, of the two mentioned components, is most likely to be causing the F.75 failure
It is possible that customers may be able to get a useful heads up via the use of the ecoTEC’s user controls, as to whether it is more likely to be the Water Pressure Sensor or the Pump, that is the cause of the F.75 fault.
Restart the boiler by pressing the reset button. On older (pre-2012) ecoTEC boiler models this is the top left-hand of four buttons located underneath the digital display. On the later ecoTEC 2 boiler (2012 onwards), it is the round button found underneath the four oblong-shaped buttons below the boiler’s display.
After the F.75 code disappears from the display and four short separated buzzing noises are heard as the boiler is going through the pre-firing up procedure, there may be an opportunity to glean whether it is the boiler’s Water Pressure Sensor, or the Pump, that is the responsible part for the F.75 fault.
Water Pressure Sensor
Shortly after pressing the reset button and with the boiler attempting to fire up, if the boiler is making similar noises and actions to that described in the sequence below, in all probability (not guaranteed) it will be the (less expensive) Water Pressure Sensor that is the faulty part, responsible for the F.75 fault.
The Pump is heard circulating water continuously through the boiler for between 10-20 seconds before stopping, the boiler then goes quiet for about 8-12 seconds. This action is then repeated, with the Pump heard running, and then stopping for a total of about 5 times. Finally, all goes completely quiet, then after a further 30 seconds or so the F.75 code appears on the boiler’s display.
If however, the boiler’s Pump has failed, this time, after the ecoTEC’s reset button has been pressed, it is possible that one of two different sequences will be observed.
In each of these two separate sequences, it is not pumping water that you can hear, but rather a faint humming type noise, this is due to the Pump being seized up and not rotating.
What is usually heard when the pump has failed, is either:
- A very faint continuous humming noise, lasting for a period of around 10-20 seconds, before the noise stops, then there is no noise at all for the next 8-10 seconds. This sequence repeats about 5 or 6 times in total, before the F.75 code appears on the boiler’s display screen.
- One long continuous faint humming noise comes from the boiler, nothing else is heard, eventually the F.75 code is displayed on the boiler. The continuous humming noise that can be heard in this “failed Pump” scenario, is caused by the Pump’s impeller in all likelihood becoming seized up or jammed. This makes the Pump get very hot, in turn giving out a faint humming type noise. A new Pump may be required if it is completely seized up.
Vaillant F.75 Fault Error Code Failure – Repairers and Costs
Who can repair this and what are the costs?
An approach that many customers have found to their advantage when first contemplating the repair of their troublesome and recurring F.75 problem, is to have a very detailed look at the different amounts charged by the various companies for a completed repair of the F.75 fault.
There are many different prices, rates and formats out there, from the big nationals, to the manufacturer, by the independent Vaillant specialist, or the local Gas Safe Registered engineer, and so on.
So it really makes good sense to drill down and work out what is going to be the best and most cost-effective option.
From a financial perspective, the price that can be paid for the F.75 repair can vary widely. It can cost anywhere up to around £300 (this being the most expensive example hopefully), where the Pump is broken and needs to be replaced.
At the other end of the scale, it could cost considerably less, possibly in the region of £110-£140 with some of the smaller operators, where it is the inexpensive Water Pressure Sensor that has failed, and is solely responsible for the F.75 breakdown.
It is worth explaining that some of the larger national companies operate what is called a “fixed price repair” charge, which includes all labour and any parts that are needed to complete the repair. This can present a reasonable option if the expensive Pump has failed, resulting in the breakdown.
However, the fixed price way of proceeding may not seem such a good choice if just the relatively inexpensive Water Pressure Sensor is the cause of the F.75 failure.
The actual cost of the replacement Water Pressure Sensor is only around £30 to £40.
So alternatively, using a Vaillant specialist, providing a sensibly-priced one-off labour charge to replace the Water Pressure Sensor, thus resolving the F.75 problem, would seem a better proposition.
Getting the repair done this way, by finding a local Vaillant boiler repair specialist, such as ourselves Glowcare (in the North West of England), could prove a much more cost-effective way to approach the F.75 fault code repair.
If your specific Vaillant boiler model is listed below, then the Water Pressure Sensor (0020059717) should be the correct replacement part number.
If, however, the Vaillant F.75 fault is due to Pump failure, then it is really important to identify the correct Vaillant boiler model.
This is because there are different types of both Grundfos and Wilo Pumps, used on various boiler models.
If the specific boiler model is known, there shouldn’t be too much confusion on which is the correct Pump required.
Vaillant ecoTEC pro 24 VUW GB 246/3-3
Vaillant ecoTEC pro 28 VUW GB 286/3-3
Vaillant ecoTEC pro 24 VUW 246/5-3 (H-GB)
Vaillant ecoTEC pro 28 VUW 286/5-3 (H-GB)
Vaillant ecoTEC pro 28 VUW 286/5-3 (P-GB)
Vaillant ecoTEC pro 28 VUW GB 286/5-3 H
Vaillant ecoTEC pro 28 VUW GB 286/5-3 P
Vaillant ecoTEC pro 28 VUW GB 286/5-3 A
Vaillant ecoTEC pro 28 VUW 286/5-3 A LPG
Vaillant ecoTEC pro 30 VUW GB 306/5-3
Vaillant ecoTEC plus 612 VU GB 126/3-5
Vaillant ecoTEC plus 615 VU GB 156/3-5
Vaillant ecoTEC plus 618 VU GB 186/3-5 (H-Gas)
Vaillant ecoTEC plus 618 VU GB 186/3-5 (P-Gas)
Vaillant ecoTEC plus 612 VU GB 126/5-5
Vaillant ecoTEC plus 612 VU GB 126/5-5 A
Vaillant ecoTEC plus 615 VU GB 156/5-5
Vaillant ecoTEC plus 615 VU 156/5-5 (H-GB)
Vaillant ecoTEC plus 615 VU GB 156/5-5 A
Vaillant ecoTEC plus 618 VU 186/5-5 (H-GB)
Vaillant ecoTEC plus 618 VU 186/5-5 (P-GB)
Vaillant ecoTEC plus 618 VU GB 186/5-5 H
Vaillant ecoTEC plus 618 VU GB 186/5-5 A
Vaillant ecoTEC plus 618 VU GB 186/5-5 P
Vaillant ecoTEC plus 618 VU GB 186/5-5 A LPG
Vaillant ecoTEC plus 624 VU GB 246/3-5
Vaillant ecoTEC plus 630 VU GB 306/3-5 (H-Gas)
Vaillant ecoTEC plus 630 VU GB 306/3-5 (P-Gas)
Vaillant ecoTEC plus 637 VU GB 376/3-5
Vaillant ecoTEC plus 624 VU 246/5-5 (H-GB)
Vaillant ecoTEC plus 624 VU GB 246/5-5
Vaillant ecoTEC plus 624 VU GB 246/5-5 A
Vaillant ecoTEC plus 630 VU 306/5-5 (H-GB)
Vaillant ecoTEC plus 630 VU 306/5-5 (P-GB)
Vaillant ecoTEC plus 630 VU GB 306/5-5 H
Vaillant ecoTEC plus 630 VU GB 306/5-5 P
Vaillant ecoTEC plus 630 VU GB 306/5-5 A
Vaillant ecoTEC plus 630 VU GB 306/5-5 A LPG
Vaillant ecoTEC plus 637 VU GB 376/5-5
Vaillant ecoTEC plus 637 VU GB 376/5-5 A
Vaillant ecoTEC plus 637 VU 386/5-5 (H-GB)
Vaillant ecoTEC plus 824 VUW GB 246/3-5
Vaillant ecoTEC plus 831 VUW GB 316/3-5 (H-Gas)
Vaillant ecoTEC plus 831 VUW GB 316/3-5 (P-Gas)
Vaillant ecoTEC plus 824 VUW 246/5-5 (H-GB)
Vaillant ecoTEC plus 825 VUW 196/5-5 (H-GB)
Vaillant ecoTEC plus 825 VUW GB 256/5-5
Vaillant ecoTEC plus 831 VUW GB 316/5-5 H
Vaillant ecoTEC plus 831 VUW GB 316/5-5 P
Vaillant ecoTEC plus 832 VUW 246/5-5 (H-GB)
Vaillant ecoTEC plus 832 VUW 246/5-5 (P-GB)
Vaillant ecoTEC plus 832 VUW GB 326/5-5
Vaillant ecoTEC plus 832 VUW GB 326/5-5 (LPG)
Vaillant ecoTEC plus 835 VUW 306/5-5 (H-GB)
Vaillant ecoTEC plus 835 VUW GB 356/5-5
Vaillant ecoTEC plus 837 VUW GB 376/5-5
Vaillant ecoTEC plus 838 VUW 286/5-5 (H-GB)
Vaillant ecoTEC plus 838 VUW GB 386/5-5
Vaillant ecoTEC plus 837 VUW GB 376/3-5
Vaillant ecoTEC plus 937 VUI GB 376/3-5
Vaillant ecoTEC plus 937 VUI GB 376/5-5
Vaillant ecoTEC plus 937 VUI GB 386/5-5 A
Vaillant ecoTEC plus 938 VUI 286/5-5 (H-GB)
Vaillant ecoTEC exclusive 832 VUW GB 326/4-7 H
Vaillant ecoTEC exclusive 838 VUW GB 386/4-7 H
Vaillant ecoTEC pure VU 286/7-2 (GB)
Vaillant ecoTEC pure VU 346/7-2 (GB)
Vaillant ecoTEC sustain VUW 286/7-2 (H-GB)
Vaillant ecoTEC sustain VUW 346/7-2 (H-GB)
Vaillant Home Combi 25 Home combi 25 -A (H-GB)
Vaillant Home Combi 30 Home combi 30 -A (H-GB)
Vaillant Home Combi 35 Home combi 35 -A (H-GB)
Vaillant Home system 12 Home system 12 -A (H-GB)
Vaillant Home system 15 Home system 15 -A (H-GB)
Vaillant Home system 18 Home system 12 -A (H-GB)
Vaillant Home system 25 Home system 25 -A (H-GB)