My oil pressure guage is not working,other guages ok. How do i

determine whether its the guage or sending unit. i don't think its a real oil pressure problem because the temperature guage shows the

car is not running hot, even after long drives.

If it were a real oil pressure problem you would hear the top end clattering.  The valve train would be making a ticking and clatter.  You would know it if you were running 0 to 5 lbs of pressure bythe sound of the top end (valve train).

You can buy a cheap guage and hook it directly to the current sender right under the hood, or you can pull in to a auto zone or chief (or equivelant) and see if they don't have a loaner oil pressure guage that you can clip in.  They may also be able to test your sender.  How much are senders anyway?  I think I'd just buy a new sender as the beginning.  Next step would be to check the continuity of the sender wire from the sender to the guage.  Make sure it's good.

Good luck.

Turn the key on.

Watch the gauge.

Pull the wire off of the sending unit and leave it open, then ground it. The gauge should go to both extreams.  If so, replace the sending unit.  If it responds but does not go to both extreams on the gauge, the wire to the gauge is making some contact, and the gauge is the likely problem.  If the gauge does not move, check the wire to the gauge, and power and ground to the gauge.