PUMA 80 pilot light problem?

PLEASE HELP.....?

Hi,

I require an experienced and competent gas engineer/boiler technician, to repair my boiler please.

Boiler: Potterton Puma 80 (permanent pilot).

Problem: If I run the hot water CONTINOUSLY for more than 15 minutes, or CONTINOUSLY run the central heating for more than 2 hours, the boiler cuts-out (with a click) and the pilot light goes out. If I then re-light it, it's back to square one.

So far, I've had two different engineers attempt to fix the problem, without success.

Between them, they have already replaced the following parts in the boiler :-

- Extractor fan assembly,
- Wax capsule,
- Thermocouple,
- auto air vent,
- flowswitch assembly,
- microswitch,
- overheat stat.

Unfortunatelly, replacing ALL of the above still hasn't fixed the problem.....

They have run out of ideas.......

Can YOU help ??? PLEASE ? If so, please leave your contact details and I will call you.


Additional info: The boiler pressure remains constant and perfect: 1 Bar with the central heating not running and 1.5 Bar with the central heating running.
There are NO unusual noises, etc. When the bolier is running it works and sounds perfect, heating works great and hot water is hot.

Also, this seems to be a WINTER-ONLY problem. During the summer, when only hot water is being used, the boiler NEVER cuts-out, and works PERFECTLY, no matter how much I use it, or how long I run it for.
The problem ONLY occurs in the winter, when central heating is being used in conjunction with the hot water.

I need your help please. Can you fix my boiler ? I can't afford a new boiler at present, so I must get this one fixed for now. Your help will be MUCH appeciated.
Please leave your contact details.

Thank You

Greg
December 2009