Vaillant 937 - Hot Water does not last for long.

[scappi3]

Hello,

I have a vaillant 937 which is about 4 years old, but has now developed a problem. When running a bath the boiler switches on and the temperature on the lcd screen goes up to about 80 and stays there for a few seconds and the goes down to 45 (which means the hot water is now nearly cold)and stays there. (The Water temeperature is set to 60).

It's almost as if it's using the water in the water tank (which is switched off).

Any ideas/recommendations would be great!

 

[bell824]

the water "tank" needs to be switched on, turn your control knob to max untill the c appears in the screen! then turn back to 60 voila hot water.

 

[scappi3]

Hi thanks for the reply.

I have tried that and the same thing happens.

We have never had the Water tank switched on, we got this feature to 'future proof' the house for when my children grow up.

 

[gazdaz36]

Possibly the shift load pump has failed.

Get someone in that knows this boiler as it's a b'stard to change