Tuxing TXED012 temp gauge

Just got my new Tuxing TXED012 compressor today. Spent the morning getting it set up and settled in. I can get more shots per fill now. Before, I would not take more than 20 shots because all I had was a hand pump and I hated spending an hour topping off my rifles. Having that compressor is going to allow me to do a lot more shooting.
I have a question about the temp indicator on top of the compressor. It has no off or on switch, works off of 2 button type batteries, has only one lead ( the wire to the temp sensor ) and the liquid crystal display stays dark. Does it show the temp only after reaching a certain level?
Any advice or guidance would be appreciated.
 
I used a 3-pin regulator to power one of my temperature gauges from compressor power. Another one, I made a switch adapter by placing two wire leads onto opposite sides of some plastic film with the wires to a switch.

Since it as so much easier to just replace the batteries, I just went back to that. Old, retired, with lots of time comes into conflict with lazy. ;)