WB Heatslave 15/19, Rads come on with hot water??

Hey all, just a quickie, i'm sure it's not a difficult question, but just need a bit of advice...... I've got a WB Heatslave 15/19, and when we use the hot water, the 3 rads closest to the boiler come on, now at first i thought it was due to the water temp being turned up to much on the boiler, so have regulated it down to the number 2 setting.

Although this didn't work , so, this is why i have decided to become a pain and make a post

Hope someone can help!!

Cheers all

Dan

Diverter valve actuator needs replacing, providing the valve spindle moves freely., (a nasty little job).

Thanks for that, i suppose it is out of my league to have a go at replacing it?? I know that it involves a drain down etc, but would it be that hard to do if i knew where i was looking? Have done a few basic plumbing jobs before i.e installing a Rayburn etc...Dont fancy shelling out £350 for a part that only costs £80ish!!

Doesn't need draining if the valve spindle moves. It's just the actuator needs replacing, but it's hidden under the control panel.