How to Replace a Mercury Access Control Board

March 16, 2026  •  14 min read

A Mercury board replacement is a two-part job: the physical swap and the software reconfiguration. The physical part takes 30 minutes. The software part depends on your platform and how well you documented the old board's settings before it failed.

Need a replacement board fast? Order from our shop. Orders before 2 PM ET ship same day. Overnight delivery is $30. Add Standard Pre-Programming ($49) to have the board arrive with your network settings already configured.

Before You Order: What to Document

Step 1: Power Down and Label Everything

Label your wiring before you disconnect anything. Use tape flags or a label maker. Label each terminal block: "Reader 1 D0," "Reader 1 D1," "Door 1 Lock," "Door 1 REX," "Door 1 Contact," etc. Take a photo of the wiring before disconnection.

Step 2: Disconnect and Remove the Old Board

Step 3: Mount, Wire, and Configure the New Board

Mount the new board. Reconnect wiring using your labels as a guide. Add the new controller in your access control software with its IP address. Verify doors, test readers, and confirm lock outputs.

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