Motorised Valve Problem

[cartman1]

I have a 25 year old heating system that has functioned fine up until recently. Occasionally now I have a problem where the heating is on at the boiler but no heat is going to the radiators and the hot water from the taps gets really hot. This happens maybe once a week now.
There's a Honeywell motorised valve in the tank cupboard and if I push the metal slider on it over to the other side, I hear a whirring sound and the radiators immediately heat up, making me think that the motor itself is on the way out.

Given the symptoms and the fact that I really don't want to have to drain the system, is replacing the powerhead with one of these a reasonable fix? I seem to remember that I did this once before, maybe 12-15 years ago.

Thanks in advance.

 

[blup]

Replace the mv, it’s had a good innings

 

[cartman1]

The whole unit (ie drain the system) or just the synchron motor within it?

Even if it's only temporary I'd prefer to not have to drain the system & mess things up at this time of the year as the wife won't be happy.

 

[Justin Passing]

If there's a pimple on top of the head, you can remove the head without getting wet. I think there's a picture here in the faq's or something.
It depends on access, but even simpler is just to replace the synchron motor:

WOw the last one I bought was about 6.99. Very cheap ones are (were) poor though.

These motors fit all the heads, but on a Hwell you'll need to join the wires iirc- so leave the old motor wires long.
You'll want a skinny T10(?) screwdriver, it's easier.