Alpha Intec 28X intermittent heating.

[SlimD]

Anyone familiar with alphas? Not worked on one before.
I had one a couple of days ago that had no heating but DHW was working ok. Problem started out intermittent then got worse until it didn't work at all.
Heating would heat up the flow to max then shut down quite quickly until temp dropped right down to about 25 degrees C. Then after a while try again. No heat got beyond the first rad.
Diverter valve and pump appeared to be ok and working.
Checked magnaclean filter and cleaned it out then heating started working fine so I assumed it was a blockage affecting flow/return.
I had also noticed that the flow temperature dial when turned made the figures on the display jump around instead of just rising or falling steadily as they should. This made me wonder about the PCB but the boiler seemed to be working normally at this point.
Customer called me today saying heating not working again and also that DHW had been playing up too, occasionally running cold.
Boiler has not shown any error codes at any point.
Anyone familiar with any common problems on these boilers that might point me in the right direction?
Thanks in advance.

 

[AMGasServices]

Have you tried to link out the external controls?

Also try running it in service mode see what it does it may give you an error code. Also if it makes a noise like a helicopter when in service mode the heat exchanger may be blocked up.

I’ll probably change the termistors for the temperature fluctuations.

 

[kasser]

You said no heat got beyond the first rad.
Sounds like a blockage in the heating system that may now have found its way to the boiler/hex to affect DHW. The boiler is unable to dissipate its heat, thus shuts down.
Or pump is not circulating the hot water fast enough?

 

[SlimD]

Thanks. I’ve since spoken to the customer again and he said it works sporadically so I’m leaning more towards a blockage too.
I think this could benefit from a power flush.