Vaillant combi no hot water

[CBW]

I'm going to call vaillant tomorrow for some advice, if they'll give it.

Doubtful, but you may get lucky.

Update
The diverter valve & aqua flow sensor have been replaced. Stills there is no hot water.

And the harness???

 

[jfg]

sorry i forgot that. all wires were traced and free from entrapment and damage.

 

[Gasguru]

Check you haven't got a mixer tap/shower letting-by, turn the cold off under the boiler and open hot taps/shower valves...do you still get flow?

 

[CBW]

sorry i forgot that. all wires were traced and free from entrapment and damage.

Might need to check the continuity and or voltage on the harness/plug. There’ll be a status code for whilst you’re running hot water, even if it’s just S.30. Also is the hot water temp set?

 

[jfg]

update after info from vaillant.

They say it's either the flow sensor or the main board.

I thought the flow sensor had been changed but there seem to be 2 fitted.
1 up top and 1 down the bottom where the cold water enters.

I think the wrong sensor was changed.

Secondly they gave us voltage readings to check.

The voltage has been checked at both cold water sensors.

The upper has 0v from the green earth. At the main board however it has 2.25v.

The lower has 4.95v at the green earth. This is the same at the plug on the main board.

From this i'm thinking that the actual lower flow sensor is fooked.

 

[Gasguru]

The lower flow sensor is for the domestic hot water, the upper sensor (that has a completely different appearance) is for the primary water flow. If that sensor was faulty the heating wouldn't work.
Have you got the old parts?

 

[jfg]

I have now sorted the issue. It was a stuck impeller.
Thanks
for all if your help

n