Review on CPS Products MT7I7A6Q A/C Manifold Gauge Set: The Ultimate Solution for Accurate Air Conditioning Readings by Richard Eledge

I've only used it twice since I bought it. He has performed well. However, there are some things you should know if you've never used one. Before inserting the quick connectors into the connectors, screw them counterclockwise until they stop. After connecting them to the ports, screw them in clockwise to activate the Schrader valve, do this slowly while watching the gauges. When you see your needles start to move, don't move more than 3/4 of a turn. If you do this, you can easily damage the schrader valve and lose all of the refrigerant. Don't let that put you off purchasing this AC pressure gauge. This is actually an advantage when connecting/disconnecting. You don't waste coolant. Before using gauges for the first time when disassembling the system. Attach pressure gauges to the vacuum pump and turn on the pump for a few seconds. Turn off the pump and see if your gauges are holding the vacuum. If not, check your connections to make sure they are loose. Last note. If you turn off the vacuum pump after turning off the system. Before the pump is switched on again, the vacuum must be relieved. Otherwise the pump may not restart. If you are new to this field, do some research on yourself before you begin.