[Shiny]

Originally Posted by JLMounce

Where I am measuring the ohm drop, is pre fuse box. I'm measuring it at the pinned connector from the intermediate harness to the dash harness, before the fuse. So, whatever is happening, is certainly happening between the pin in the lamp harness and the intermediate harness.

Would it be worth it to load the gauge at this connection? I know the sender measures too low here but you could verify the gauge calibration after you fixed the ground and put it all back together. There's always a chance the issue is up there. Honestly, you said the gauge reads 1/8 to 1/4 low. That is 11 to 22 ohms off if the reading is directly proportional. This is inconsistent with the 4 ohm error you found. Maybe there's more to it?

A dead short should be empty and full should happen with a load of around 90 ohms, right? A few resistors in between wouldn't hurt and if it all tracks, you will at least confirm your fears about the wiring.

Mike