Glow worm compact 80 e hot water problem

Good day to you all

I am posting this question for my brother in law, who does not have acces to the internet at the moment.

He has just(last tuesday), moved in to his new house.The boiler that is there is a glowworm compact 80e.
It is giving him some trouble.
The problem is that when he demands hot water, 2 out of 3 times the boiler will light and give hot water, and the other time it will not light at all.

Is there any quick checks that can be done before calling out an engineer.

Regards

Grajam247

first check - system pressure needs to bejust over 1 bar.

Thanks for the reply.
The system pressure was about 1.5 bar

There is now a different problem.
When we tried to put the boiler on for central heating,it fired for about 45 seconds then shut itself down.

I think that the BIL is going to get someone in as he seems to think that it could be the PCB.

Regards
Grajam247