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I'm looking for information. On the 69-71 d series with the oil light the housing is different from the oil gauge housing but what about the wiring? Is the wiring for the light and gauge the same?

I know that the sending unit is different between the light and the gauge, but I'm not sure about the wiring itself. I would assume it's different since the connections would be different between the back side of a gauge and the back side of a light bulb.

While the wiring isn't identical, it serves the same purpose in both cases, that being to complete the ground circuit.

With a light, the wire acts as ground & illuminates the light when there is no/low pressure. Once there is oil pressure then inside the sending unit the circuit becomes open & the light goes out.

With a gauge the sending unit varies the continuity of the circuit, based upon pressure. The wire just acts as conduit.

Bucky

I was curious. There's a harness on eBay and when I asked gauge or light I was told same harness P/N for both.

O.K. I finally changed the instrument cluster housing to one that excepts the oil gauge. The light unplugged from the harness leaving two wires, one white and one black. The black wire was a power source while the white wire went to the oil sending unit for the light. I got a oil gauge wire from Bud which plugged right into my original harness and changed the sending unit and voila working oil pressure gauge. Not very hard at all. If anyone is concerned by the age of this post/ thread it really does take me this long to get things done.