A worceter hiflow 400 hot water problem

[col810]

Hi,can anyone help?
I have a worcester hiflow 400 which gives out scolding hot water.I cant seam to be able to adjust the temperature of the water.Its stone cold or boiling hot.The water control switch doesnt seem to do anything other than boiling hot or freezing cold.Is there a dodgy thermostat needing replaced or is it something else??

 

[kevplumb]

the hot water temp sensor is on the hot out pipe FWIW

 

[COG]

If its an old 400 and not a 400e then you have no hot water senser just a hot water thermostat that controlls the heat at the slave tank in the boiler so at min the slave tank will be 54degC app and at max 82degC, so it controlls the amount of hot water not directlt the temp. The senser fitted to the hot water outlet pipe is an anti scald stat set at 70degC this interupts the hot water stat .

 

[col810]

So why is my water scolding hot all the time??
The control knob is switching the water temp on and off instead of controling the temperature needed.

 

[ChrisR]

We're not psychic!
Knowing something of how it works, someone will have to diagnose the problem with a multimeter and surface thermometer. It could even be the track behind the knob is cracked.
If you aren't happy to work on the "technology", don't touch it.