room stat not calling for heat

[fatpiemanpaul]

hello all
i have a problem with a room stat in my house.Set say at 20 ,all is well.Once temp is reached the boiler turns itself off.As the temp in the house falls the stat does not call for heat at all,the boiler stays off.There is a 3 core cable at the stat,and i realise that 1 of these cores is not connected right at the junction box .Please,can anybody enlighten me .
It is a very old glo-worm 45 back boiler,gravity hot water,pumped c/h.
with a honeywell v4073A 1039mid position5 wire motorised valve, cyl stat
honeywell L641A1039 prog ,potterton EP2002 &pump.
Thank you

 

[craig51]

Are you any good with a multimeter??

First would be to check for continuity and open line while amking and breaking the switch (or 240v - 0v when making and breaking the switch)

THis will then rule out the RS.

 

[garyhoborn]

can also do it dead with electricity off - a lot safer - test for cont when switch is made

 

[craig51]

can also do it dead with electricity off - a lot safer - test for cont when switch is made

Like i said

 

[garyhoborn]

is the white wire in the junction box live when heating is on and room stat high?

 

[bengasman]

... i realise that 1 of these cores is not connected right at the junction box .

What makes you think it is not connected right?