FC Oil Pressure Gauge Failure
 

Wasnt really paying attention to the gauge so i dont know when it happened but my oil pressure gauge dropped below zero so i know i have pressure its just somthing broke. i changed the gauge cluster out but no dice. the needle is way under zero just resting at the bottom. i traced wires and found what i think is a ressitor on the master cylinder. when i changed it out it work for a lil bit. it went to the correct pressure and next time i went to drive it, it was no longer working. now can the part that reads the pressure broke? and i believe its the peice thats round brass and the wire slips over a nail head. thats what it looks like. any help will be great.

Yes, the mushroom shaped thing threaded into the rear iron is the oil pressure sender. Check this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/oil-pressure-sender-915757/

The "resistor" is actually a condenser. Check this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/condensor-grounding-capacitor-oil-pressure-sending-unit-question-174742/