AC low side pressure is too Low — What it means when AC low side pressure is too Low
If you’ve attached gauges to your car’s AC system and the pressure readings are steady but the AC low side pressure too Low, here are the possibilities:
Possibility #1 AC low side pressure is Low because the system is undercharged
If the engine is running and your gauges are showing low side pressure too low and warm air is coming out of the vents, the system may be low on charge.
Possibility #2 AC low side pressure is too low because the expansion valve or orifice tube is stuck closed or clogged
In this case, the compressor is running and try to remove refrigerant gas from the evaporator. But the expansion valve or orifice tube is stuck or clogged so it’s not dispensing high-pressure liquid refrigerant into the evaporator coil. In other words, the compressor is sucking, but there’s nothing to suck.
Possibility #3 AC low side pressure is low because of a restriction on the high side
As in the condition above, the compressor is running and trying to suck refrigerant out of the evaporator coil. However, if there’s a restriction on the high side of the system in the receiver/dryer, a crimped tube in the condenser or crud accumulation in the condenser or the expansion valve or orifice tube, there’s nothing to suck.
©, 2020 Rick Muscoplat
Posted on by Rick Muscoplat