You need to check your hot water tank to see if you have one valve with 3 pipes connected, or 2 separate valves, each with 2 pipes, these will be just past the pump.
If you have one valve I suspect this is stuck, if however you have 2 valves it is possible that the motor in the valve for hot water needs replacing.
the battery is to keep the memory in the timer in the event of power fail.
gary.wright53@googlemail.com, June 2007