Promax/ Performa hot water switch

[Stanios]

I am sure everyone is familiar with these and the common diaphragm replacement cure for drips and no hot water fix.
Just the other week replaced a diaphragm it looked pretty good I put new one in anyway. The pin did come out but only when the tap was half way on at least. Pressure in the house is normal. With new diphragm nothing changed, about 10 l/m pin just about starts to come out but not enough. To add to the problem sometimes even on full hot water mixing in cold will cause the pin to receed and hot water goes off..

Checked the two tubes for blockage, cold inlet too. So am stumped. Any help would be appreciated!

 

[Aquarius]

Could it be corroded slightly? Looking at that setup.

 

[PETE 123]

Is there a filter on the inlet maybe part blocked.

 

[Last Plumber]

Have you checked the pressure differential waterways for blockages inside. The water ways are only very small and if one is blocked you won't get the alteration in pressure needed to operate it. Also if they are OK, check the other end where the two small bore tubes connect in. It only operates off a differential in pressure as you may know so there has to be a reason for not getting the difference if it has a new diaphragm which is seated correctly.