TriPac APU heater problems

I found 1 for $25 (pic attached) but when I removed it today it was just like this 1:
https://www.dieseldash.com/TK420978-thermo-king-engine-temperature-sensor

$146 original TK, and I can’t seem to find chinese one that looks exactly like that one on amazon, looks like the one on amazon is different so Im confused. And then reading this here got me even more confused:
Tripac AP1 WT1 Error Code 249. Engine coolant sensor

 

Sht now that I did some more research - I never bled out the air in the TriPac not once since Ive been having coolant temp issues, multiple times coolant would flush on its own. So Im hoping its not the temp sensor thats bad but the fact I have to bleed out the air in the system while refilling the coolant. Maybe this is why the Tripac keeps shutting down on me?
How to do it if anyone has the same issue as me:
https://www.thermoking.com/content/...ts/TriPac Closed Loop Cooling 55827-19-IM.pdf

 

Wait what? I can use the Espar heater by itself - without having the APU interfere, and all I have to is buy the Espar controller? I hate my APU turning on to charge the batteries in the middle of night while using the heater, I doubt they would even go low
enough to the point where my trucks batteries would go out. I most use the Espar 8-10 hrs 2-3 nights a week during winter.

 

This is a good option to have. I might do this if my apu acts up again. Concerning the battery, its basically like the Chinese diesel heaters - just works off the battery and fuel. The truck would low voltage disconnect if the heater used up too much of the battery while the heater is working through the Espar controller?