hot water no heating vokera linea 24

[leon]

am working on the linea 24, boiler fires up fine on hot water on heating mode the boiler fires up then reaches temperature in about 30 seconds. Have checked pump which is ok also checked for a blokage on the return isolation valve as seemed like a circulation problem flushed water through the return pipe work. Problem stll occuring followed fault finding flow charts in manual. When i remove the power head off the three way valve the boiler fires up and the temperature display falls. i have tryed replacing the power head and the pcb, have checked modulator coil and there is no voltage across the terminals am thinkng that the gas valve may need replacing, any ideas

[htg engineer]

Have you checked gas pressures ?
Sensor or thermistor faulty ? cutting boiler off too soon ?
Check flow through heat-ex, very hot ? possible blockage in heat-ex ?

So from cold, you put the boiler on the radiators don't heat or very little ??
does the flow pipe from boiler get hot ?

Diverter choked ? or faulty, you've changed the head what about the valve itself ?

htg

[moger4]

i had this problem , the divertor valve itself is stuck , i got a service kit and fitted it and it run fine the rod gets caked in scale and sticks , you have to clean up (greese the rod with silicone greese) and replace all the kit parts and it runs perfectly after that