Vaillant F.0 fault - NTC open ciruit?

[Grangey]

Hi all,

Been having a few issues with my Ecomax recently, mainly down to my ignorance on servicing.

Anyway the boiler has now been serviced (professionally), and was working fine until recently where it gave up the ghost and displayed F.0 (which I've never had before (previously I was dealing with F.24 mainly due to sensor issues).

Now I've recently replaced 2 NTC sensors based on the feedback from my previous thread... seem I missed one though as there was a 3rd hidden away, so I'm hoping that's the culprit.

I've also just replaced the wiring loom (this needing doing, but for clarity the fault displayed before I replaced it, as well as the cable itself that goes to this 3rd NTC sensor), so it's definitely not a cable fault.

I'm just wondering before I get my hopes up on replacing the remaining NTC, is there anything else this could be?

Pressure is good, and can see nothing else obviously wrong (bar a small drip leak from the connection which has holds the filter which I'll be addressing at the same time as replacing this NTC).

Thanks!

 

[Grangey]

Update, 3rd NTC replaced... no difference. F.0

Literally out of ideas now, anyone have any suggestions? New loom, new ntc sensors, still F.0 Fault.

 

[MeldrewsMate]

What is your system pressure?
A quick search on the Vaillant website told me F0 refers to system pressure which is too high, or too low.
This could be because your system pressure is too high....... or too low.
It could also be that your pressure transducer (sensor) is playing up.

Your use of the word 'literally' is unnecessary. It is a word reserved only for the use of teenagers in every sentence (should they feel inclined to grunt out a whole sentence), along with the mandatory 'like'.

 

[Grangey]

Hi Meldrews, where on the Vaillant website did you find that? I've only found F0.0 relating to NTC faults..?

Pressure is stable, I've adapted it between 1, 1.5, and nearly 2 to ensure it wasn't this but it's had no effect. But, if it is pressure sensor related, thats something I'm happy to try, but couldn't find anything suggesting it (pressure seemed to be F25 faults)

 

[Grangey]

So looking at the manual, I thought I saw a clue... F.0 clearly stays is a "FLOW" NTC fault, only I can't quite work out which of the NTC's relate to flow, as in the same manual, they're just called temperate sensors... I think it's number 6, but that's the one I've replaced today with no difference

 

[oldbuffer]

The NTC on the flow pipe is number 6 in the diagram. However, in the troubleshooting guide the problem may relate to 1 (or more) of 4 problems. Assuming you have replaced the NTC itself then the problem could be the connection to the NTC itself, its connection at the board or a broken NTC cable. If you have a multimeter with resistance and continuity reading, you could check the following (all with the boiler electrically isolated):

1. Disconnect the plug for the NTC from the NTC (if it is plug connected), and likewise disconnect the plug from the board (again if plug connected). Check the continuity of each side of the cable. If either side does not show continuity, replace the cable.
2. Measure the resistance of the NTC. It should be about 2,000 ohms at 25 degrees, dropping to about 250 ohms at 90 degrees. A mug of 3/4 boiling, 1/4 cold tap water should give you about 75 degrees, say around the 450 ohm mark. If the limits are out by more than about 15%, replace the thermistor.

If neither of the above identifies the problem, then it is probably the board. Then its time to call in an expert.

 

[MeldrewsMate]

Hi Meldrews, where on the Vaillant website did you find that? I've only found F0.0 relating to NTC faults..?

You're right, I said it was a quick check, but failed to notice that the 'too-smart-for-its-own-good' software on the AskVaillant website had changed my 'Vaillant F0 fault' enquiry to 'Heatline F0'. Bizarre but true, so ignore my last post, and there's nothing in the MIs fault list relating to F0 for the EcoMax.
Have you tried phoning Vaillant tech help for a description of what the boiler thinks an F0 fault is? According to your diagrams F0 relates to temperature sensors only, or the main pcb. Measure the resistance from the point where the NTC sensor wiring connects to the main pcb, at least then you'll be able to determine whether it's a sensor/wiring loom or a pcb error.