Thermostat

[addo]

Try actually boiling the thermostat in a saucepan on your stove. It needs to be fully covered by the water.

Also make sure you're fitting it the right way around...

[Oldpug]

This is strange? I would be very surprised if the new stats are faulty.You have a circulation problem but what is causing it seams to be a mystery? I would suggest a blocked rad` ? but that does`t happen overnight,its a gradual thing.Remove the rad give it a flush out,think of something stupid like something trapped in a hose or what ever.After refitting the rad remember to remove the bleed tap on the n/s of the rad when filling up.

[myglaren]

If the 'stats aren't opening in boiling water they must be faulty.
There may be other issues too but that needs to be eliminated first.

[addo]

He didn't say he actually boiled it - he dropped it in some just-boiled water.

It's got enough thermal mass that the resultant temperature might readily drop below opening.

I'm still calling pilot error.

[wulfgar2k]

IT'S FIXED Well here goes, Sunday mourning go to a new spares shop ask for a thermostat tell him all about the problem found a thermostat i said to him " i do not want that one" because it the same batch number as the one i have and they do not work so loads of huff and puffing we found one with a diffrent batch number, i will have that one...
BINGO IT WORKS so if it's new it may not still work so be carfull
so new thermostats can be FAULTY
First line thermostat ref FTK 073 Batch Number G3474..BEWARE
Thanks for all your help

[Peter.N.]

Well done Phil, that could have caught anyone out.

[Oldpug]

I did say "try something stupid" but I would not have expected that.What a pain and a waste of your time!! but its nice to see its fixed.