Micron pressure gauges can help monitor pressure and temperature changes when attached to an AC unit. A system fault could trigger wild changes in the pressure values displayed by the micron pressure gauge. When an issue develops, it could be down to the reasons in the YouTube video “HVAC Vacuum Problems: 5 Tips for a Micron Gauge Reading Jumping Around!”
Water in the system is a major cause of wild changes in the micron pressure gauge. When water enters the system and is near the vacuum pump outlet, it could get pulled out by the vacuum pump, leading to a wild drop in pressure reading.
Similarly, oil in the evaporator coil could trigger wild pressure changes. The oil blocks space in the coil by moving side to side, leading to pressure changes in the micron pressure gauge. A technician should perform an oil blowout procedure to solve the issue.
A dirty vacuum gauge with oil can also cause wild pressure changes. Cleaning the gauge sensor with alcohol could solve the problem. Intermittent leaks at the surface valve or hoses and locking off the refrigerant inside the system can cause micron pressure gauge issues.