I cannot turn off my Triton Ivory II shower?

I cannot turn off my Triton Ivory II shower, unless I turn off the water supply to the shower. Turning the electric source to the shower off makes no difference, water still pours out. I have checked the solenoid resistance and that says it is 3.64, above the 3.5 that I understand it should be for the solenoid to work, can anyone shed any light?