We have a 16 year old Hansa thermostatic mixer over our bath/shower. The tap was leaking constantly so a plummer capped the shower and bath exit lines. A second plummer attending to another issue found a feed back loop to do with the hot water and the mixer. We now have a kit to fix the mixer but cannot get any hot water.
Is there a separate hot water control where the hot water enters the mixer control valve that could have been screwed down or closed?

Hi Pickles

Most tempering (or mixing) valves are adjustable via a nut or cap on top of the valve. Here, you may just need to twist the cap or you may need to loosen a screw and then pull up on the cap to be able to make the adjustment. Hopefully, you have instructions nearby (or can get them online). Otherwise, have the plumber come back and make the adjustment so it is set at a temperature not to exceed 125F to the entire house (bath valve should be set at not to exceed 115F if possible).

Good luck!

Mark