Low hot water pressure

Hello, if anyone can help it would be greatly appreciated.
I have a Pulsacoil 2000model APC2015, it is approx 7yrs old.
The probblem I have is the hotter I turn the hot water then the pressure of water reduces to probably half what it used to be, this applies to all taps including shower. I have checked the header tank and this approx half full, I do very occassionaly have the Manual Overheat reset Thermostat trip out which then requires resetting, this did occur twice in quick succession recently during the very cold weather.
I have also noticed the main circuit board LED flashes around 7times (very fast) a second.

I am in Welwyn Garden City (near St Albans).

Kind regards.
Paul

Change both sensors.
PHE and DHW.
Should be the answer
Mike
MGC/H2O
Norfolk.

Mike, thanks for the reply.

I would like to change the sensors myself, would you advise this as being ok?
I notice the DHW (hot) sensor is screwed into the Heat Exchanger pipework, will this require the system to be drained when removing/replacing the DHW sensor? Also my PHE sensor appears to just 'push' in to a pipe section is this normal?

Kind regards,
Paul

To change the DHW sensor, turn off the water supply, open the hot taps.
Lay a towel over the pump.
Remove the DHW sensor. Wrap PTFE around the thread of the new one. Install and wire in.
The PHE sensor is a push in.
Put the sleeve over to keep it in and tight.
Mike
MGC/H2O
Norfolk

Thanks Mike.

Don't over tighten these as it cracks the pipe or snaps the sensor heads.