Diaphragm Issue??

[John506]

Just been to take a look at my uncles boiler which isn't giving him any hot water. Boiler is a Vailiant Turbomax.

Upon turning on the hot tap, the diverter valve doesn't make the switch, nothing moves, nothing happens.

I then turned on the hot tap and manually pushed the switch down myself, and there was still no hot water.

Is this likely to be the diaphragm or the microswitch, or both?

Thanks,

John.

 

[MANDATE]

I would say the diaphragm is most likely holed.
Before you turn on the hot tap the diaphragm has equal pressure on either side of it. Opening the hot tap releases the pressure on one side so the the diverter now moves due to the pressure on the opposite side.
As the diverter goes to hot water position it triggers the micro switch to fire up boiler.
With a split/holed diaphragm the operating pressure is lost through the split and diverter does not move or moves very little.
Also, you can always test a micro switch with a meter

 

[Agile]

Easier to test the microswitch by pushing it with a screwdriver.

Commercially I always change the whole diverter valve as otherwise an old one is likely to fail or start leaking.

Replacing those is not the easiest of jobs for a DIYer and several aspects can easily go wrong!

Tony

 

[bazdaman]

Does the boiler even fire when u manually make the switch?

 

[J_N30]

If the boiler doesn't fire when you manually make the switch there's a different problem altogether.

You run hot tap and switch doesn't make, you need a new diaphragm. Bit of a pig on these not for the diyer.

But sounds like you have more problems anyway. Does the heating fire up?