Here's what I have...and it makes me really wonder.
On one of my engines...a Perkins 6.354 circa 1979.... I replaced the oil pressure sending unit. That was a while back....but what I have found, is that it appears that the wire from the sending unit has gotten very hot and looks a bit cracked and charred.... Not good I know.
Actually both of my sending units were replaced at the same time, and I have not had the same happen with the other engine.
Now....with the engine running, oil pressure gauge on, and alternator on (alternators on both engines triggered by oil pressure)...I can wrap my hand around the wire that appears burnt....and there is absolutely no heat from the wire.
Whats really a bummer....is that I cannot remember what the wire looked like when I put the new oil pressure sending unit on the engine.