Hot water running hot and cold - upstairs only

Hi,

I own an IDEAL MINI HE C24 COMBI BOILER.

I recently had a leak which resulted in my 3 way diverter valve filling with water - this has now been replaced.

However...

The HOT WATER in my bathroom runs hot then goes cold, this seems to be caused by the flue in my boiler sparking up and going out constantly when the hot water upstairs is running.

This is only an issue with the BATH - the bathroom sink and all downstairs are fine.

Can someone please help!!

Thanks[/quote]

Haven't a clue. Just wanted to share that with you.
Commonly you get on - off - on behaviour if the flow is reduced - eg at showers. Presumably your bath flow is more than the basin?

Try reducing the water flow at the bath to roughly match what you're getting at the basin.

boiler overheating?

Shoots upto 90degrees as soon as you turn on the hot water - flue goes out, temperature drops down to about 60 and the water runs cold.

Faulty thermostat perhaps - or a slow motor?