I know we don't know anything about one another, it is something that makes discussion forums difficult sometimes. So, don't take offense to what I say.
When the cooling system is full and stays full and is parked on concrete for days and no drips of anykind, then I typically don't look for a leak in the cooling system, because it is not loosing any coolant. Again, no offense to anyone. But I check the system - held 15PSI for over 4 hours - good enough for me.
As for the "stack"- I simply shined a bright flashlight into the bottom side and moved my head around looking for light through the stack - no problems there .
I have crawled around under this unit and there is no sign that this thing was every driven in anything that would even take the paint off. So I was not to worried about debris being between the cooler and radiator.
So these are the reasons I did not mention the basics to start with - sorry.
Followed the test procedures for the gauge and did all the stuff listed above in the post and the bottom line is that their test procedures are not complete as far as I am concerned - it said the guage was good - read nothing when disconnected and pegged when shorted - in between open and closed seems to be where the problem lies.
I installed a totally mechanical gauge and drove the heck out of it - engine heats up and cools down perfect as far as I can tell - fan kicks on at 200 and off at 190. Brought he sending unit in and got out the thermometer and meter - according the resistance chart above - it is within 100 ohms of working correctly. That could be just my meter or thermometer being off .
It seems that it is the meter itself, but at this point I think we are going to install the mechanical meter and put a led bulb in it that will work on 24 v for lighting.
The more I get familiar with this, the better it looks.
I truly thank you for all your help on the heating problem.
The build will move forward - it seems strong when driving it - shifts firm. The steering pump seems loud and might have a small leak. I will be changing all the fluids in everything when we get to going on the build. We just wanted to make sure we did not have lemon before continueing.
If any ideas come to anyone, send em. I think the tank and pump install will be pretty straight forward. I am putting thought into the lighting - I want to see if I can get lights or make lights or modify lights to go where they already are - but have all the warning lights in them and not have to run a lot of new wires. I have an old 18 wheeler that is hard to find turn and headlight assy. So when the turn signal lamp holders broke out of the plastic, I took 5 led button trailer markers, drill holes, heat stakes them in and now I have better turn signals - and saved about 550 per side on headlight assy.
Has anyone seen any of these with warning lights in the factory lights?
Thanks again.