Oil pressure gage

[brownac1983]

Ok, so my oil pressure gage is reading low, even after a full rebuild with a Melling oil pump. I have good oil pressure, have installed a new sending unit, and it still reads low. I have 15 ohms at a high idle from the sending unit post to the grounded shell of the unit. According to an earlier thread I found, the high mark should be 10 ohms, and 15 ohms should put me above 3/4 of the gage. When I ground the terminal connection to the head, the gage pegs, as expected. My other gages read okay, so I don't think I need to adjust the voltage regulator. Is there a way to adjust just the oil pressure gage? There are two wires going into the back of it, a white and red striped wire with a white boot, and a black wire with a black boot. If I was to run a jumper wire straight from the sending unit to check the circuit, which terminal would it go to? Last, does anyone have a instrument panel schematic for the trucks with oil pressure gages? The only one I can find is for the trucks with temp lights. Thanks.

[68F250]

There is an adjustment for the gauge only, but it's been so long dang if I can remember the details, you use a jeweler's screwdriver.

You can test the accuracy of the gauge using resistors in place of the sending unit. 10 ohms = full, 22.8 ohms = midscale, 73 ohms = empty.

[brownac1983]

Thanks. I got it. You have to pull the gage and there are two little holes on the back of it that have teeth inside them. By adjusting those teeth, you move arms that adjust the low stop and (i think) range. My low stop was off, and the only thing stopping the needle was the fact that it bottomed out mechanically. I set the low stop at the low mark, and it works great. It still has a bad connection at the sending unit though, I think I'll put a new end on it tomorrow.

[68F250]

Super! Where did you find the info?

[brownac1983]

Found the info for the fuel gage here in an older post. I figured the oil gage must be about the same. It was. Credit to Jarrad. He explained it really well, and I found everything just like he described it. Actually, I see that the link you posted in the same thread covers calibrating the gages, too.
http://www.fordification.com/forum/view ... &&start=15#