Possible diverter valve problem

[matt1976]

My boiler is a Vaillant Turbomax Pro running on natural gas.

When i turn on the hot water tap i get a bit of hot water then it goes cold. I have looked at the diverter valve pluinger through the inspection hole and it isn't moving when the tap is turned on and off. But if I turn the boiler off completely and then on again the plunger goes down and I get hot water. As soon as the heating comes on the plunger pulls back up and there is no more hot water until the boiler is power cycled again.

Is there any way of checking what is going on? Can I test the valve is getting power? I take it this is a good first step to diagnosing the problem.

The only extra thing I have noticed is it the plunger doesn't seem to go all the way down the first time but eventually hits the end stop. It moves all the way back up in one go though.

Thanks in advance

 

[matt1976]

I just need a way of diagnosing if the problem is the valve or something else. I've seen they are a common part to fail but don't want to change it for no reason.

 

[kev_1911]

have you taken the moterised head off and checked to see if the pin travels fully in and out? if not then take it off and turn the tap on or get sombody to do it whilst you watch the head,if it moves all the way in and out then its the rubber ball in the diverter valve that will be sticking......change the valve.

 

[matt1976]

I've tried it again now the system has cooled down and it works fine. I take it this means the ball has cooled down and shrunk enough it has stopped sticking. Explains why it works ok in the morning for a shower but not in the evening to wash up.

 

[Agile]

Explains why it works ok in the morning for a shower but not in the evening to wash up.

Simple solution then!

Wash up in the morning!

Tony