Vaillant Ecotec combi boiler - radiators working but no hot water flow to taps

Boilers are inherently dangerous for the average DIY for so many reasons, contact British Gas and have them come back and fix it, tell them it was fine before the "service". They may simply have a control valve shut off.

If you they won't go off when your timer is off. There's a possibility it's clock keeping it on although its turned off, which is fairly rare. However depending in which model of Vaillant you have, if your boiler has a hot water pre-heat on it. Some models which have this the diverter was prone for sticking thus leaving the port for the radiators open when in hot water mode.

Oh some of these there was a small black heatexchanger just for hot water they some times block up . or it could be a blockage in the water section where it flows in .I know Valliant have a very good tech line and fitters who do house calls .

We have just had our old system boiler replaced with a vaillant ecotec plus 837 and sounds like a similar working operation to ours. At first I was a little concerned,but I was told by our installer that he was told by vaillant that these very latest boilers size the system on start up for about 10 mins, then take temperature to target flow which you set boiler at. So even by setting target flow temperature very high you still get the initial sizing cycle, which ours was about 30-35c temp. These boilers seem to run biased for efficiency as after a while they modulate the boiler burner down and the radiators run more on the side of warm than really hot like the old type boilers. You also get better efficiency as at lower temperature the boiler condenses better. You will also find you get a more constant temperature in your home rather than over shoots. I was concerned at first, shame there was no info/explanation in user manual as people do need to know that this is normal operation. We are used to ours now, took a month and by the way these boilers can make a creaking noise but was told this normal expansion/ contraction but annoying when sited in bedroom cupboard. Best of luck!

you need a new dhw thermistor

Hi ,

Can you please tell me the model of the vaillant, and the approx age?

I can solve this problem

I await your reply

Thanks

Steve :)

Most likey problem is the diverter valve, not energising fully. This in turn will not move the little plastic lever arm that actuates the microswitch on the side, sending the signal to ignite.

You can buy a diaghram kit from most local plumb centres, you need to replace the diaghram and seals, don't forget the silicon grease to ensure the plunger doesnt stick. Kits less than a tenner.

You should have noticed before it stopped working completely the water had reduced in temperature before the weeks it failed.

To make sure it is a diverter valve fault, depress the microswitch if you can, when the hot water is flowing and hey presto the demand for hot water light should shine.

when the tap is turned on and the water light on the boiler doesn't this means the diverter valve is not operating it could be down to low water pressure in the house this can be checked at the cold tap in the kitchen. if there is plenty of pressure then it could be the diagphram in the diverter valve is worn or split. the diagphram is only a few pounds but it depends on the engineer you get as to how much money he wants to fit it.
the egg timer symbol (or two pyramids together) is an ignition indicator turn off and on again to see if it will fire with the tap running. reset the boiler with the lower right hand control knob.

Which turbomax, as there a two different models. The more modern one, with the brass CPL diverter valve, located at the front left of the boiler, was very prone sticking & jamming, this would restrict flow through the hot water circuit in the boiler, and cause cycling. Vaillant actually modified the diverter. You can identify, if it is the old type, as there is a very small hole in the middle of the diverter on the old ones, probable no more than 1mm-2mm wide. The modfied one, is much bigger approx 5mm wide. If old type, replace as this usally sorts the problem

does the boiler come on when the hot water tap is run if not change the hot water flow switch or the diaphram in the hot water flow valve it may be split