My old Slime Digital Sport Tire Pressure gauge not working. I think it needs batteries. I opened it up and the batteries were bad. I bought four new LR44 batteries from Dollar Tree for $1.00 (Daiso store also sell watch batteries) and after that, I cleaned the metal contact, install the new batteries and the gauge comes back to life again. (2 batteries on top and 2 batteries on bottom).
If you only have 2 batteries, then use it on the bottom, the one next to the display and connected with the light/tube. The "top" two batteries are for the light (the one on the plastic cover).
I understand the batteries will fall off after you opened it; therefore, the last minutes of the video are the pictures for the position of the batteries (+ or ).
After that, you can slowly put it side to side and the close the case.
If the light did not work, you may have to turn the screw a little tighter so that it has good contact or add little paper behind the metal on the batteries so that it can push against the board to have better contact and less room to move around.
Thanks for watching and one less ewaste in landfill.