Thanks for your help, however I have a question about the positioning of your diode. As far as I can remember, current will try an continue to flow in an inductor if interupted suddenly (hence the arcing at the contact). Fly wheel diodes provide a path for this current to continue to flow once the contacts are open, preventing the arcing. from your diagram it looks like arcing would continue to occur as there is still no path for the current to flow into the solenoid, apart from acrodd the open contacts. Before reading your post i would have put a diode between negative and terminal 3 of the relay, providing a loop for the current to flow after the contact has opened. However I do see that the positioning of your diode will prevent spikes going to the power supply. Am I missing something?