Myson Apollo 40Si fan sticking?

I hope somebody can help with this.
We have a Myson Apollo 40Si which began to not come on automatically unless we bang the casing, at which point the fan begins to run and it lights up. We thought it must be a fan problem so fan was changed but problem remains. Also, when the boiler is running, it continuously short cycles off and on every 10 or 15 seconds or so. I changed the diverter valve as that was definitely faulty and checked pump runs properly so I don't know what else it can be. Anybody know what it can be?..Any help much apppreciated.