I am seeing this strange behavior in my oil pressure guage in my 96 2500 Cummins Turbo Diesel, and wonder if it might be a bad sending unit, or a more serious problem. What it does is drop down flat on the peg when I accelerate even a little, and when I let off the throttle it goes back up to normal, in the middle of the scale. This started happening only when I ran the A/C, but now it happens all the time. Oddly, even when it's totally bottomed out and on the peg the oil light never comes on, so is the oil pressure really dropping like that, or what?

Can anyone give me a clue here?

Thanks in advance,

Amy