Heigh Ho Fellows

I've a 58 Merc. M-100 Truck w/ a 223 I-6 & the Oil Pressure Gage was not working.

I replaced Both the Sending Unit (which the parts store guy stated was correct for a gage & not an idiot light) & the Gage which I was able to locate N.O.S. replacement.

Now on Start Up the Gage "pegs" all the way over to the right.

Now, does this mean I have the "incorrect" Sending Unit for my Gage or do I have a Short that I have to Locate now or possably Both?

 

I would be suspect of the sending unit. Supposedly the idiot light sender is smaller with a cylindrical business end a little bigger than about 1 by 1 inches; whereas the gauge sender is much larger, closer to 2 by 2 inches at the business end and is tapered or somewhat conical. But a short likely would also peg the needle.

 

Yeah, the idiot light sender will definitely peg the gauge if it's set up for the real sender. I soldered across the resistor in the instrument cluster before I changed the sender to the real one in mine and it pegged high. Normal with the right sender (much bigger). The idiot light sender is about as big as your thumb.