Y-Plan valve - knocking noise

[rossani]

I installed my CH/HW system around 18yrs ago and it's been pretty trouble free. Recently, at the point the HW switches in, there is sometimes a regular knocking noise (around every half second), which continues until I turn the HW off at the controller. If I turn it straight back on the knocking noise does not reoccur. The noise is fairly light and appears to be coming from the Y-Plan valve. I've replaced a couple of Syncron motors over the 18yrs due to humming, but I've not heard this knocking noise before.

Does anyone know if it's likely to be the motor again, or possibly the valve itself?

Thanks

 

[nickso]

synchron gear could be slipping on the toothed spindle plate.

 

[rossani]

Nickso,
Are you thinking that that might make the valve inside keep bumping, or are you suggesting the noise is the gear slipping?

 

[nickso]

im saying the noise could be the gear slipping.

if the valve is constantly moving back and forth and hitting one of the microswitches on and off all the time its the valve electrics at fault i believe.

 

[rossani]

Sounds as though it would be worth the replacing the motor again and see if the problem goes away.

Thanks for your help.