Central heating strange problem

[tommyk1981]

I live in a ~20-25 year old house, with original central heating system consisting of a Honeywell programmer/thermostat/motorised valve (a V4073A 1039) with a Myson Compact CP53 pump.

We've just gone to put the heating on in the past few days and noticed that none of the radiators were heating up, at all. Odd, as this was working a few weeks ago.

I've checked the following:
- All radiators have been bled
- Heating is switched on at the programmer
- Room thermostat is set to 30 ("clicks" around 15 so should be sending an "on" signal?)
- Manually opening the valve sets it all off, and the pump gets going; if I hold the valve open for a few minutes, the bottom of the first radiator starts getting warm
- The above suggests that power is getting to the units (the pump and valve come off the same power supply it seems - a white box attached to the floor of the airing cupboard)

I have noticed there is a little leak from the seal at the "bottom" of the pump (I think it's the egress side) which in the few minutes I had the valve manually open, produced only just enough liquid to form a drop at the bottom of the pipe - not even enough to make that drip off.

I also noticed when bleeding the radiators that the pressure wasn't particularly high - when I've done it in the past it's always fizzed out, but this time it just dribbled out really...

So, any ideas? I've had a look for a pressure gauge on the hot water tank and the boiler but no joy... I'm starting to worry that it's a sludge problem, however the water that came out of the radiators was clean..

Thanks in advance for any help!

 

[sparkybird]

from an electrical point of view, just because the thermostat clicks doesn't mean that it's switching the power on/off. Do you have a multimeter? You can open up the thermostat (with the boiler switched off) turn the dial up, switch the boiler back on and check between switched live and earth to see if you have 240V