[bestgenman]

Revisiting the "air in the coolant" again, my post meant to say "the highest point in the radiator hose".  The petcock Pt is referring to is on the top of the thermostat housing (if my old memory is correct) and getting air from underneath the stat is very difficult.  This is why a tube 2" long of the same diameter as the hose with a petcock soldered in works the best.  I does away with trying to force water into the system to evacuate the air.  Th air will work it's way to the highest point (where this new petcock is located) and just cracking open the petcock will let the air escape.  True, it does take a while but works much better than  the petcock on top of the housing.

In response to your second thermostat.  The controller uses a grounded signal for shutdown on pressure and temperature.  these switches are paralleled rather than seriesed.  Any grounded sensor will result in a shutdown.  I believe PT uses an ambient air temp switch inside the enclosure which is connected to the HWT shutdown input on the controller.  High ambient temp appears as HWT since there is only one input.  Since your enclosure fans are not working, your enclosure temp exceeds the switch setting.  Resolve the enclosure cooling problem and then tackle the coolant problem.  Or, unplug the ambient switch but keep in mind these are installed to protect the engine and disconnecting could cause a scored piston so, be careful running with disconnected switches.  Keep your guard up!!

I'm not aware of any sensors on the "head" for these sets.  If it were a 2000KW set, it would make sense.

I can send you a wiring diagram if you let me know the model of your set.

You are on the right track, keep at it and your be successful.