Thermostaic shower - hot or cold only

[groganpaul]

I bought a thermostatic mixer shower. It will only give cold or hot water no matter what temp is on the dial.

If you turn the temp all the way down its cold. If you turn it all the way up, its hot.

If you set it at mid-point its either hot or cold (depending on whether it was last set at the hot or cold position)

If you turn the shower on and try to get the temp to change it will stay stone cold up to a certain point, then only give hot water. The same happens if you go from hot to cold water.

I read it may need a booster to equalise the hot and cold pressure. A dual booster has been fitted and it still wont control the temp.

Any thoughts?

 

[picasso]

hot and cold the wrong way round ? should be hot on left as you look at it from the front.