Oil gauge question

[cstiles]

so I need some help. My truck is a 81.My oil pressure gauge stays on the highest it a go to which is right at the 3 o clock position when the key is on. It really doesn't move much when I turn the key off either.it doesn't have a sending unit hooked up.. that's how I got the truck .but I did buy a sending unit and hunted threw wires but had no luck .someone told me what color wire it should be but I can't even remember now and apparently they were wrong. Does anyone know what color wire I should be hunting or if not having the gauge hooked up a makes it pegged or if something else causes that . All the other gauges work so I wouldn't thank its the cluster.

[bd]

The pressure sender connects to the oil pressure gauge through an 18-gauge tan wire.  Two possible sender locations are at the back of the intake manifold adjacent to the distributor or at the left rear side of the engine block directly above the oil filter.  The gauge points to 3:00 o'clock, because the sender wire is disconnected.  Wiring diagrams are located near the back of the 1981 Service Manual.