You zero the gauge by pressing the stem in the gauge port. If you use the rubber plug in the back of the gauge and it may leak out some fluid out. My Kennedy gauge that I’ve had for 14 years never zeroes out and has always read a little off.
As for the pictures I’m assuming one picture is the pressure with the pumps on and the other is the picture with the pumps off? When you zero the gauge does the needle actually go to zero?
As for the pictures I’m assuming one picture is the pressure with the pumps on and the other is the picture with the pumps off? When you zero the gauge does the needle actually go to zero?