DT90E Firing Heating On when Timer is Off

[DIYNick]

I have just fitted a DT90E thermostat to me system replacing a T6360B.
All is well, with the wiring as it had four wires bit I removed the earth and neutral to install the DT90E so only have live and switched live now.
My problem is that even though the timer I see off, I can turn on the heating system by increasing the temperature.
Can anyone explain why and tell me how to sort this please.?

 

[CBW]

What timer is it? What boiler/system? Did this not happen before with old thermostat?

 

[D_Hailsham]

how did you identify which were the live and switched live?

 

[DIYNick]

Hi both, thanks for the reply.
This did not happen with the previous stat, all worked ok. The controller is a ST699.
I identified the live and switched live from the wiring instructions of the old stat and also confirmed on the web but it shouldn't have power if the controller is off so wouldn't matter if they were the wrong way around.? However I will check this.
The boiler system is gravity and I attach image of the 699 wiring
I appreciate your replies.

 

[D_Hailsham]

The ST699 wiring looks OK. It tells me that you have a mid-position valve controlling CH and HW. However, in addition to the expected link to terminal 5, there is an extra red wire connected to terminal 8 (HW Com). Do you know where it goes?

Which boiler do you have (make and eact model)?

Do you have a multimeter, and know how to use it?

 

[DIYNick]

Problem solved, thanks everyone.
It was a faulty programmer, the switch is faulty and although not lighting the led was permit voltage to thermostat.