Boiler failing to respond to thermostat and has to be restarted

[stevered]

It has become a common occurrence that my boiler is failing to respond when the thermostat kicks in.

I hear an audible click from the heatlink when thermostat is turned up but nothing else happens.

Our heating programmer next to the water cylinder is set to continuous and all looks OK.

The only way to restore central heating is to turn the boiler off, which in turn powers off the heating programmer and pump. Turn it back on and then it fires up.

Worth noting the central heating pump is coming on when the heating is off for long periods of the time now it is cold but I believe that is just the boilers first protection kicking in as it is in the garage so will often drop below 5c.

Any ideas what could be causing this?

Here is my setup;

Vaillant EcoPlus 430
Nest e thermostat and heatlink
Honeywell ST9400A programmer
Grundfos UPS2
Honeywell V4073A1039

 

[Knappers]

I would get rid of the programmer that you don't need, you can get poor connections that cause issues and it's really obsolete isn't it?
Usually these faults are to do with 3port tho.
New head or maybe just new syncro motor will do it. Can check with voltage on orange from 3port - if not 230v when on then that's the issue.