How do I wire a new pump if the new one has an extra wire?

Andrew,

There are, no doubt, many 'experts' available through this AskMe service, but I somehow doubt that any of them are expert mind-readers. So perhaps you'd like to give them just a little information about your problem so they can try to help you...

Brand/model of air-con?
Number and colour of wires on old and new pump motors?
Was the replacement pump purchased from the manufacturer (or agent) specifically for your model of air-con, or did you buy some third-party pump just hoping it might suit?

Daniel