Chasing an inoperative engine temperature gauge

[Arnie C]

So when I bought my truck, the PO had clipped the wires off the coolant temp sensor and mumbled some gibberish about needing to get a sensor from International. Truck still runs fine, doesnt overheat, etc but I would like to have a working dash gauge even if it is just for idiot lights.

I found the cut off end of the pigtail in the storage area behind the rear seat and soldered it back on. I am 98% sure its original. The wire colors match and it looks like it has the same amount of use/discoloration as the rest of the harness.

I plugged in the sensor thinking that maybe the guy was an idiot and the gauge in the instrument cluster immediately went to full hot with the engine cold.

I went to the Ford dealer by my house and got the correct sending unit per the parts man and noticed a few things.

1. My harness did not plug in. There was an extra tab on the sensor from Ford. The connectors did work but I had to force it.
2. My temp gauge read half way up when the engine was cold. I swapped it on a warm motor, and as soon as I got to the end of my block, it was pegged out and the check gauges light came on. My truck doesnt overheat.

So I am left with a wiring issue, gauge cluster issue, or a bad sensor.

Does anyone know the proper ohm range for the gauge cluster on a 2002 F250? Any suggestions?