I purchased a replacement outside air temp indicator for my '87, and find that the only way I can use it is to also update the 4-pin plug in the vehicle with the newer 5-pin plug. I can't find either plug in the EPC (although doubtless it's there somewhere).

Strangely, the relevant service manual page shows the older setup as having 4 wires (which it does), but has them connected to pins 1, 2, 3, and 5. Pin 5 doesn't exit on the older gauge. Has anyone replaced their older 4-pin gauge with a newer 5-pin unit? How did you wire it?

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Rob