TriPac APU heater problems

-It blows a lot of thick white smoke once I turn it on
-If the truck is off - the heater doesn't even turn on, just cycles on and off and shuts down
-If the truck is running for about 10-15mins and I turn on the heater - the heater turns on and works. Then I shut off the truck. After a few hours (battery goes low?) the heater shuts down, and I have to turn on truck again and restart the heater.

Any ideas what’s going on? I’m close to ordering the Espar maintenance kit and replacing the gaskets, cleaning the glow plug, and replacing the glow plug stainer/screen.
Im thinking that would take care of the white smoke, but still not sure why it only turns on while the truck is running and shuts off after s while?

 

Yea

 

Whats the reason the heater wont fully start working unless the truck runs for a while - the carbon buildup? And why does the heater shut off after a few hours? The APU isnt kicking in therefore it shuts down? The batteries are 2 years old so doubt theyre the issue

 

I believe it starts and runs a bit and turns off abruptly almost as if something is blocking it from running its cycle fully to the point where it charges the batteries like it should.

 

I did it 3 years ago but barely put on any hours on it since then, since I did local. Even my AC on it doesn't work. It turns on but shuts off after a few mins with codes:
93 Low Pressure Cut Out
6 Failed Water Temperature Sensor WT1
18 Shutdown High Engine Coolant Temperature

Not sure if that has any play here as well with the heater but maybe? Will most likely plug it in my laptop and see if it brings up any codes with the heater mode