Help required with Thorne Apollo

[Sheltie]

My old Apollo was working fine up until a few days ago when it went out & the pilot refused to stay lit when I released the valve.

I replaced the thermocouple & the pilot head with no improvement. I eventually managed to get the pilot to stay lit when I short circuited (for testing) the interuptor on the Thermocouple.

The boiler now has a pilot light, when I try to fire it up it sounds like the main boiler is lighting (woof) but there is no hot water circulating. After a few minutes the overheat cut-out appears to kick in and the whole thing (including the pilot) shuts down with a loud click.

I have also noticed that the pump appears to be permenently running when the power is applied to the boiler - irrespective of whether the boiler is (or has been lit). I have tried setting the 3-way valve to manual but cannot seem to get any water circulating.

I appreciate that I will have to bring in a (Corgi) engineer but would appreciate any opinions as to my problem.

Obviously the thermocouple interruptor will require changing and it could be that the pump has also packed up, but would a failed pump cause it to appear to be running continuously or would some other fault cause this. Bear in mind it was working fine up until a few days ago and I cannot believe that multiple critical faults have all occured together.

Any help would be appreciated.

 

[ChrisR]

Not all of the above can be true (surely!).
If after the woof it overheats , but nothing's got hot??
The pump's running, but there's no circulation?? At all??

Have you done anythng to let air in??
Could be coincidentally short of water - bled any rads?
Check header tank.