No offense meant but are you sure you are testing the right wiring? 4.5 is @ ref voltage if the you are testing the right wiring then it must be shorted or crossed somewhere.
Sorry for my ignorance, but what do you mean by @ ref voltage?
I'm fairly sure I am testing the correct wires. I was checking between the red and black wires. When I applied 12v to the seat wiring directly from the battery the seat worked fine. I will check again though.
Thanks for the link to the wiring diagrams. I printed the relevant one.