Oil Gauge issues

[mixman03]

ok first post
so the oil gauge in my 89 supra na went out first i turned the key start the car and the gauge shot straight up to the max then slowly went down all the way to zero, and stays there did that for about a week but now it just stays at zero no matter what i havent replaced the sending unit yet but am going to but i was wondering if there was a way to test the gauge itself to see if it still works? someone told me try grounding it, i tried nothing, is it just the one wire comming from the sending unit that goes to the gauge? basically i wanna make sure it works before i go through the money and trouble of replacing the sending unit any help is welcomed

thanks you

 

[87GWSupra]

If you ground the wire to the pressure sensor it takes all the resistance out to the gauge letting it shoot up maxing out the gauge. If the gauge sits grounded for to long it will fry it just like you would with any short to ground. I'm thinking it is most likely your gauge. I would also check the wiring very closely for any damage where it can short.