Glowworm Swiftflow 80 not heating water. New fan fitted.

[nez_bit]

7 Year old glowworm swiftflow 80 (honeywell) has recently got a bit noisy and last week, out of the blue stopped heating either when the hot water is on or when the central heating is on. It sounded like a classic fan issue, so I've changed the fan for a new one. It worked straight away for about 5 minutes, but then stopped again. It came on again for 5 minutes after about 15 minutes of being off, and as of now comes on every now and again for the heating, but not as it should, but never for the hot water. Can anyone help from here. When the system has been off for a while, if a open up the hot water, i get scalding hot water for a second or two but then straight back to cold, even when the main nurner has not been on. The pilot light always stays on and never goes out.
I think that the pump stays on and can be heard vibrating a little but never goes off. The fan does go onand off as required when the burner cuts in, but when the burn dies out, the fan slows but the pump keeps going.
As a further note, I've checked the flow valve and the sensor is making a circuit when the hot water is pumped through.Also, the pressure on the pressure on the system seems to be going down quite quickly.
Hope someone can help.

 

[nez_bit]

Pressure sorted. Turned it up to 3 then released it quickly. Seems like the release valve didn't shut properly but does now.
But we still have a boiler that doesn't fire. Any ideas?

 

[nez_bit]

Had a man round today. Scratched heads a bit. Now working, but only after pressing on the PCB. it seems that only half the board was working before that, but now it seems o.k. Fingers crossed. I'm assuming it is a possible dry joint underneath but has anyone else got any ideas?

 

[Agile]

Monologue?

 

[nez_bit]

No, just keep adding bits in the vain hope that someone may helpwith my problem. I've took the PCB out this morning as it all failed again overnight, and there are a couple of dry joints, one especially bad around the flow switch points. I'll try and solder and test from there.