Actuator noises

[Ladybird]

We have a Grandee oil-fired combi boiler which seems to be working fine but the actuator in the airing cupboard makes a very loud whining noise every now and again.
We turn the heating off to stop the noise (afraid to leave it making this noise for too long!) and then turn it back on after a couple of minutes and it is fine. Any ideas what may be causing this - is it serious and will it be expensive to fix?

 

[wilhelm]

not serious, either change valve head or the motor therein.

take valve head off. see how stiff the operating pivot is to turn. you may need a new valve complete

if this does not make sense . get someone in.