[alsalp]

Originally Posted by Peter Serio

"I noticed that when I tried to use the harness or even having just the circuit board attached "the other two" would get "excited" when test a given gauge. What does this mean? The circuit board checks out. Using TU5, 185 deg is between the first two marks. 200 deg is at 1/4 mark, and My propane burner maxed at 206 with reading about in the middle of 1/4 and 1/2 marks."

I was not there right beside you when you were doing these tests but I think I know what you are saying. All 3 gauges in the #1 circle opening share a common power supply (key on) thru a 15 amp fuse. And all 3 share a common "reference" ground at the rear steel panel that they are bolted into. However each gauge seeks more information than just those 2 connections. Powering up gauges with a open sensor string can damage that gauge. Both the oil pressure and the fuel gauge in particular. There is no car condition ever that either of those two gauges would see infinity, it's as if their sensor wire was un-plugged. Making tests running 12 volts battery + thru the printed circuit as power MUST include completed sender strings for all 3 gauges. Otherwise you can damage a gauge. A string (1 each per gauge) would be your variable resistance box terminating to ground. That is why I have a total of 3 separate decade resistance boxes on top of my workbench.

So if I create a common ground through the shell and the CB I need the "other two" getting simulated or sender resistance while test a given gauge?