Baxi solo 50 rs low flames inside boiler

[spanners57]

hello,
my boiler has just this week stopped heating the rads, only luke warm. you dont seem to hear it ignite to heat like it was doing. one row of burners lights first, then about 30 secs later the other row lights, but when you turn the control, it doesnt make any difference to the heat.
2 months ago, a new gas valve was fitted due to a leak. boiler has been working ok up until last weekend.

any ideas???? please

thankyou spanners

 

[Boilerman2]

Get the RGI who fitted the Gas Valve back, these boilers are sometimes slow to "cross-light", the new valve may be faulty, or just needs more setting up its a job for a RGI