Vokera Aqua Nova not working properly

[TheOldBarn]

My Vokera Aqua Nova water heater is not working properly: when I turn on a tap the water slowly gets hotter to about 45 deg C then goes cold then gets hotter and so on. I can hear a switch clicking in the unit as it is doing this. If I turn the tap off the unit's fan continues running for a while. No warning code is displayed i.e. the green light flashes throughout. The temperature control seems to make no difference.

The unit is about 3 years old and I don't think it has been serviced (I only just bought this house). I took it apart and cleaned out some dust but this made no difference. Burners look clean and clear (we run off an LPG tank) and so does the flue/fan assembly.

 

[DP]

What is the light sequence on the front panel when it does that?

 

[TheOldBarn]

What is the light sequence on the front panel when it does that?

The Green light comes on continuously for a while, then goes back to on for one second, off for four seconds, then comes on continuously for a while, back to flashing, and so on. The Red light never comes on.

 

[DP]

Solid green is burner on.

Flashing every 5 seconds is no demand.

Have you tried other taps? Are the taps fully open?

 

[TheOldBarn]

Solid green is burner on.

Flashing every 5 seconds is no demand.

Have you tried other taps? Are the taps fully open?

Yes, thanks, I read the manual and saw that this was the meaning of the lights. I've tried all 4 taps fully open, and the shower. The flow seems to be fine.

 

[DP]

If flow is OK, have you checked the connections and voltage at the flow switch?

 

[TheOldBarn]

If flow is OK, have you checked the connections and voltage at the flow switch?

Thanks: Just checked this and there appears to be no voltage at the flow switch. What can cause this?

 

[DP]

Take the wires off and check for a short crcuit.

I little thank you goes a long way too