A class sp overheat led

Hi there.
Recently moved into new house.
I have an a-class sp, with flashing overheat led yet everything seems to be working fine.
Pressing reset will reset the unit but immediately flashes the overheat led.
There are no fault/ error codes stored.
Called technical and was advised new PCB.
Tried new PCB, married it to the unit but the primary pump is no longer running yet the dhw pump is now constant and still the overheat led flashes.

I have ended up refitting the original board and revered back to where I started.

What am I missing here?
Any help greatly appreciated

Check the store sensors x 2 off
Check the overheat sensor x 1 off.
ACB might not come up with fault code.
Check sensors for being stiff should be supple cables.
Check for any water ingress in the dry pockets
Also wiggle / tap the sensors in case of bad wire / connection etc.

Check unit is full

Check all pumps are free and have water

Fault code 10 would be overheat

Trying running the DHW on the timer and see if it makes any difference.

Could be dirty pipes from boiler to unit.
A failing pump.

Mike
MGC/H2O
Norfolk

Hi Mike,
Appreciate the reply.
I should have also mentioned I visually inspected all the sensors in the dry pockets prior to further investigation and found the top one missing the thin "spring" piece that holds the sensor in place.
I had replaced this sensor before the PCB but to no avail.

Both pumps are running free and strong. (Upon demand)
Original PCB runs the primary pump as expected but new PCB was running the dhw pump instead. (Also the front reset button wouldn't work with new PCB)

The inbuilt programmer buttons don't really seem to be doing anything, if I call for heat at the room stat, I get heat. If I open hot water tap, the dhw pump kicks in and I get hot water. Regardless of programmer position.

I have just swapped the boiler from ideal to baxi ecoblue advanced and flushed system so I know it is clear.
The unit itself is full as I drained off and watched the expansion tank refill.

There is no error code recording on either PCB just the annoying led keeps flashing.

I have the boiler set to approx 70°c so I know it cannot possibly be overheating.

Well your boiler should be running at 80c

The store will never be satisfied with the boiler at 70c

Mike

On DHW you would normally be on constant.

Heating can be timed or constant.

DHW is on demand at the taps just like a combi.

As long as the unit is hot that is.

Mike