Potterton Promax 24 HE - Funny Noises!

Hello...

My boiler has started to make 'wind / whirring' noises. It doesn't happen constantly, but for about 5 minutes a time.

We have recently had £400.00 worth of maintainance carried out, with the electrode kit and syphon kit being replaced - not sure whether this is relevant!

Any ideas on what the wind type noises are? I'm in the process of selling my house and could do without having to spend more money on the boiler!

Many Thanks in advance.

I should probably add that the boiler makes a load bang before firing up too!

The obvious answer would be to recall the firm who did the maintenance as it sounds as if it may not have been done properly or something else may have failed.

BG do a fixed price repair for about £200 so £400 sounds quite expensive.

Tony