What is wrong with my boiler - hot water only occasionally, heating fine?

this is due to blocked heat exchanger. its a very common fault for glowworms to block up quickly. even if u change the part a year later u be back here. if u look to change the boiler make sure u add inhibitor to the boiler and top it up every 2 - 3 years as this will prevent this problem in the future. intergas is a good replacement as they use a diffrent technology to warm the water so it wont face a similar problem

kash
January 2013

Always found glow worms to be ok.
What does not happen, what happens when you ask for HW? Low temperatue would indicate a faulty thermostat in boiler, But, What else is happening. Basically, when you open a tap, the boiler sensor operates, telling the boiler to switch on, It also changes the water flow via the divertor valve, so that the cold in will go via a heat exchanger and out to the tap with sensors to check temperature of water out matches set temperature. None of those parts are expensive, Well a dealer will tell you they are, divertor valve was recently quoted at about 200 to replace, with the recomendation of new boiler, New valve £40 fitted myself easy, sensors, few Quid each Main thing that could be wrong is cct board, Ebay £60 new. OR less. Use your manual, that you should have, IF not get one from glow worm, listed under literature, Lots of fault finding to back. Also tells you basic how to replace items.

SD
January 2013