Hi my sister had a ford fiesta 1.4 tdci 2007 , i looked at it it has ac which is not functioning ,it seesm to me that it could be an electrical fault , has anyone a diagram of the wiring ? does the 12v supplied to the pump / elcetromagnet come via a relay ? can i test for 12 power to unit , i should see 12 applied when ac switched on ? As i dont hear any noise from unit or change in rev from engine when i press the ac button on in the car , thanks