Possible Sensor(s) Not Working - Help needed

I have a Boilermate 2000 without a switch.

Recently we have had trouble with out central heating coming on and then going off intermitently and our showers/hot water also being hot for only a short period of time.

Our Potterton Central Heating system does ignite but only for a short period of time and then it turns itself off and then after 30mins or so it comes back on, during this time the radiators heat up but then cool down again with it is off, resulting in our house never getting warm.

I have been told that it might be a problem with the sensors on our Boilermate. I therefore took off the front over and pushed the buttons to check the temps as per the manual. The Store, PHE and DHW sensors all show temps between 48 and 55, i believe these should be a lot higher? No errors were shown.

My main question is how can I tell which sensor, if any, has failed?

Slight update.

I left the heating turned on yesterday all day to see what it would do. It had the intermitant switching on and off for most of the day until around 2pm when it appeared to stay on.

I went back to the Boilermate and looked at the diagnostics, storage was showing 70+ while the other two were still in the 50s.

Any help appreciated.

Bm 2000.
It does appear that the main ACB has failed.
A common fault.
Heating stays on whether;
Time clock off
Room stat off

If you had read through the BM 2000 posts you would have found your answer.

Mike

Thanks for the response.

Slight problem in that I never mentioned that the heating stayed on.  In fact if I turn off the time clock and room stat it goes off as per normal.

To summarise the problem is that the central heating and hot water do warm up but they take forever to do so with the central heating turning itself on and off over a period of approx 5 hrs until it is up to normal temps.

Oh and I have the read the other posts but nothing appears quite like this.

Oh I forgot to mention, although it is in the book and on here.
The heating Will not work if the store temperature falls below 60c.
So forget about the heating.
Heat the store up first.
Check the boiler pump is operating.
Voltage and has water.
I assume you have checked the F & E tank.
Water level?
Unit takes water?
How old is the unit?
Mike

Can it be Potterton boiler problem? It doesn't stay on for a long time that's why it takes forever to bring store temperature up to the level. Overheating sensor in boiler is faulty?

Could be Potterton boiler.
Not a favourite boiler to say the least!
It could also be,
The boiler pump on the unit is tired, old or worn out.
Or the boiler to unit pipe work is sludged up thus impeding the flow from boiler to unit or return from unit to boiler.
Or the heat exchanger on the boiler is sludged up.
Check / test those.
Mike