Working fine for years. Hot water OK, No errors codes shown. This is an intermittant fault, but frequently the central heating system will begin to work, then suddenly, stop.
The temperature climbs rapidly to 75/80 degrees, then the pilot light switches off, the heating cuts out and the temperature drops back to 35 degrees within seconds. There is then a wait of approximately 2 mins and then this cycle of climbing and falling repeats seemingly indefinitely. Consequently, it fails to draw water around and the rads dont heat up.
The hot taps run fine without issue. If i switch the boiler off for a while and turn it on again, it begins to work once more until this fault starts up later on. I've bled all radiators and there was very little air to come out. The boiler has also made an angry growling noise on occasion. I've had a technician come out to check it but frustratingly, whenever he arrives it's working again!
Interestingly, when the heating is working, the pressure is at the top end of 2 bar, but when it's not, the pressure is just over 1.
Any help greatly appreciated,
Adam