Hello,
I searched back through some of the earlier posts before posting this, and it seems that everyone else has the opposite problem to me. When I adjust the temperature control, the water pressure FALLS as I reduce the temperature setting. The hot and cold pressure at the bath located next to the shower is good. I have another shower downstairs with an identical mixer, and there the pressure is constant over the temperature range.
I've used a thermometer to check that the actual temperature is correct when set at the safety stop of 38C. At this temperature, the pressure is very low, and it increases as I increase the temperature to its maximum.
Could it be that the cold water inlet is partially blocked, and so causing a reduced pressure at lower temperatures?
Any ideas, many thanks, Paul