Presuming your old Tekonsha controller has the following wires and the same shaped plug (see link) it should fit: Black - Battery Power Red - Stoplight Signal White - Ground Blue - Output to trailer
What is the old Tekonsha model. Tekonsha have used the same socket at the back of the controller for years. I would not get too hung up on the wire colours, someone may have used different colours to wire your up in the past. However the socket pin arrangement has not changed over the models where the same plug has been used.
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
What you are proposing is exactly what we did some 4 years ago. For memory the older controller does not have a plug just the 4 wires coming out of unit. So it would only be necessary to connect these to the 4 wires on the plug to convert to the new controller.