What does abnormal AC manifold gauge readings mean?
How to diagnose car AC with manifold gauges
Low side low/high side low: system low on charge
Low side reads 15-30-psi and high side reads 110-150
Low side is low. High side normal to slightly low
Low on refrigerant charge
Restriction in the low side of the system causing evaporator starvation.
Restricted or plugged orifice tube
Problem with expansion valve
Moisture in the system. Moisture collects and freezes on the expansion valve or orifice tube, cutting off flow of refrigerant into evaporator.
To test for moisture: Turn AC off for 10-15 mins, then back on. If gauge reading goes back to low low side reading, the orifice tube or expansion valve screen is likely plugged. If the gauge reading is normal when first turned on and stays normal for a few minutes, you get cold air and THEN low side goes low, that’s a sign of moisture in the system.
Evaporator icing due to starvation. Refrigerant dwells too long in evaporator and picks up superheat causing the evaporator to freeze and restricts airflow. Turn off AC and leave blower on high to melt ice. Once airflow comes back turn AC on. If the cycle repeats, the evaporator is icing up. Caused by low charge, low airflow (plugged cabin air filter), faulty expansion valve sensing bulb or faulty evaporator temp sensor.
In an expansion valve system where the valve is located on the evaporator outlet
Low side VERY low/high side low: restriction
bbbbPosted on by Rick Muscoplat