Yeah I've seen this happened when I did a motor swap and kept the oil and water sensor from the other vehicle they were setup for warning lights and sent a constant signal to the gauges saying they have pressure or good temp. The gauges are expecting a pulse signal instead of a constant signal. Long story short try swapping one of the two senders with one you know is meant for a gauge and not a warning light to rule it out. I'll try to find you a part number, but your local parts store should be able to tell you.