omega estate window screen washer motor?

I have an omega estate 2001 the window screen washer works fine on the front but on th rear it does not work I have change the motor (motor works front and back) Does anyone know if there is a relay and if so where it is. Forgot to mention that I had a test bulb on the two wires, the front lights up bright but on the rear very dim.

Paul
September 2009