How to fix vokera mynute 16e boiler??

Boiler switching on and off every 5 mins, and turning itself on when timer set to off. Changed the ntc sensor / thermister sorted problem out, took about 30 mins to do, its located on the right of heat exchange at the back behind copper pipe.

mycrapboiler
January 2011

Had similar problem with my Mynute 35e. In my case the ignition would go on and off every few seconds. When opening up the boiler one of the relays on the main PCB could be heard vibrating. This only happened when the boiler had been on for a while.

In my case it was the main PCB but I managed to fix it without buying a new board.

Don't try this unless you are confident handling PCBs and working around live mains. With the boiler running and the fault occurring use freeze spray on each chip, transistor and diode on the main PCB, slowly one at a time. When I got to the chip labelled SP2 the relay started behaving.

Got the data sheet for this chip from the internet, got an equivalent chip from RS components and now the boiler is working. Cost me 20p for the replacement chip.

In my case the chip on the Vokera PCB was CNY75GC and I replaced it with CNY174X. This is an opto-coupler.

Martin
June 2010

It's the thermistor - I had the exact same problem a few years ago. "Qualified" person told me it was the Printed Circuit Board, despite my arguing with him that I thought it was thermistor (he didn't take too kindly to a female having an opinion on his area of "expertise"!) I replaced the PCB and the problem still existed. So got a new thermistor, fitted it and has worked fine since!!

Sinead
January 2010

Ignore the assertion that you may not open the boiler case if you are not gas safe registered - it's a load of tosh put about by people who are Gas Safe Registered and do not properly understand the regulations - badly informed probably.

You may not mess with boilers for money without being Registered - the only requirement if it's your own boiler is to be competent - the regulations do not define competence.

http://en.wikipedia.org/wiki/Gas_Safety_(Installation_and_Use)_Regulations_1998

It may make sense not to remove the cover but there is absolutely nothing to prevent or to censure you if you do.

Peccavi
November 2009

deos the flow or return get very hot,if so then the over heat stat is cutting the bioler off.this means there is a cerculation problem.can you hear the pump running or feel it working.try bleeding you rads if the pump is working to remove some of the air lock.remember if you are not gas safe registered,you must not open the bioler up.Advice is free

steve singh
November 2009

check the water press first before you do anything on the water gauge if it reads below 1.5 mbar top it up to that some biolers will go ot lockout pressure falls below a certain level to protect itself

max
November 2009

sorry cant give you much help on this - obviously overheat stat kicking in so COULD BE a circulation problem where radiator water is not being pushed around system and overheating quickly this could either be the pump not moving or is too slow or something in system is stopping it (ie diverter valve or assoicated controls) Turn all rads on full room stat to high turn on ch only to see if it works Then try just with HW on only to see if bioler ignites Whatever happens you gonna a need another visit from engineer to check them out sorry i could not be of much help

max
November 2009