Systemate 2000 Intermittent hot and cold water from shower and taps

We have intermittent hot and cold shower water problem, same problem affects running a bath. Local heating engineer recently ran diagnostic test and located an error on T2 sensor. Sensor has been replaced and tested, all was fine for 6 days. Same problem is now back again, the same heating engineer has returned to test again and all tests show the system is working fine. Clearly it is not, but what can the problem be? Central heating appears not to have been affected. The problem occurs whether the heating is on or not. Sometimes it's only the first shower run that experiences the problem, sometimes it's only the second, sometimes both (as it seems to be now). If we put the emergency back up hot water on then showers/bath are fine but this is a longterm expensive option.

Please can you offer any advise, as on Segel there doesn't appear to be a Gledhill specialist in West Sussex and would like to get some clearer idea of problem so I can get the right engineer in to fix.

Hope someone can help.

Hi,

Sadly your technician changed the wrong sensor. It is the T1 sensor that usually causes the problem you have, although either can do it. I suggest getting the T1 (DHW, the upper sensor) changed as well.

Cheers, Mike