Testo 552i Wireless Vacuum Probe

So overall this is a good unit. I was slightly hesitant to buy a gauge that was 100% Bluetooth with no built-in screen. So far that hasn't been an issue and I do like being able to monitor it from inside the building or my truck. I believe the gauge is accurate and effective. I did originally have one major issue while learning how to use it. You must not get any refrigerant or nylog inside the probe. Apparently I got some nylog inside the fitting and it gave some bizarre readings. Look at the screenshots. I cleaned the unit with 99% alcohol I connected it directly to the vacuum pump and cleaned it out. Afterwards it was good and reliable. One big note! Do not apply excessive pressure to this probe! 300 PSI will destroy the gauge. I usually apply 10 PSI of pressure to the system before disconnecting the vacuum gauge to prevent contamination. Once it's disconnected I then charge the system to the maximum.