Thnx folks, An infrared therm is next step. Z thank you for the info. The GP harness is brand new, ( original harness replaced) which I thought would cure the issue. Then there was the collapsing upper radiator hose. And then both two pin sensors were replaced. Only the four pin remains as factory.

Yet, there is no other evidence of a failed pump or thermostat. I beleive it all electrical. Temps were at over 100 when I got home. Upper hose was warm to touch, intake mani was still near cold! This morning after a five minute run, 120, but the upper rad hose wasn't even fully pressurized and intake still cold! AAAARRGH!

Good news is I have until next spring to fix it , replace the condensor and recharge the AC.

Given that the wiring harness is brand new, where would the short be? It does trigger the aux fans, which is why the brand new aux fans are now unplugged. This leads me to believe it's not the guage ground itself.

These old "simple" diesels are not so simple to diagnose, are they!?