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Andrew Smith
Andrew Smith, Plumber
Category: Plumbing
Satisfied Customers: 3757
Experience:  City and Guilds qualified plumber
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Help. My M90F 28s has packed in. Flashing red light. When i

Customer Question

Help. My M90F 28s has packed in. Flashing red light. When i press reset the red light goes out and the boiler whirs away ten seconds and then stops again with red light. No hot water neither. How do I put the boiler into diagnostic mode.

I hope I am not just paying to show me how to do a diagnostic?

I am hoping we can find the problem.

Submitted: 3 years ago.
Category: Plumbing
Expert:  Andrew Smith replied 3 years ago.
***** ***** : If the fan is running and gets no further then you have a problem with the air pressure switch
***** ***** : Are you able to take the case off and check this?
***** ***** : If you come back to me I can help you but it sounds like you will have to check a couple of things inside the boiler.
JACUSTOMER-835xxnq7- :


JACUSTOMER-835xxnq7- :

Boiler has been working intermittently. What I have discovered is that when i press the reset button, while the boiler is whirring away, if I turn on the hot water tap, the boiler will fire, and keep running hours before locking out again. If I don't turn on the hot tap, the boiler just whirrs away to fifteen seconds, then locks out again.

***** ***** : Are you able to check the pump is spinning?
JACUSTOMER-835xxnq7- :

Yes the pump is definitely running. I think it may be cutting out on high limit. My wife has been turning down the TRV's on the radiators, and I am wondering if it does not have a bypass, and there is not enough flow sometimes to stop the water temperature getting too high. I have turned the stat on the boiler down, slightly, and open all the rads fully, and I will see tonight when I get home if it is still running, (it turns on about 5, and I get home about 6).

***** ***** : Good idea
***** ***** : Let me know how you get on