What Causes No Pressure in the Low Side of a Car's Air Conditioning System?
3 Answers
Generally, it is a fault with the air conditioning compressor, where there is internal leakage within the compressor. Replacing the compressor in a timely manner can resolve the issue. Below is more extended information about car air conditioning systems: 1. Components: A car's air conditioning system typically consists mainly of the compressor, an electronically controlled clutch, condenser, evaporator, expansion valve, receiver-drier, hoses, condenser fan, vacuum solenoid, idle speed controller, and control system. 2. Refrigeration System: The car air conditioning refrigeration system is composed of the compressor, condenser, receiver-drier, expansion valve, evaporator, and blower. These components are connected by copper pipes (or aluminum pipes) and high-pressure rubber hoses to form a sealed system. When the refrigeration system operates, the refrigerant circulates in different states within this sealed system. Each cycle is divided into four basic processes: compression, heat dissipation, throttling, and heat absorption. These processes repeat continuously to achieve the effect of lowering the temperature of the air around the evaporator.
Last time my car's AC wasn't cooling, and I couldn't get any pressure reading from the low-pressure side. Experience tells me this is often due to insufficient refrigerant or a system leak. It could be aging connectors leaking refrigerant, or the compressor might have internal issues preventing it from drawing in refrigerant. I tried some basic checks myself: start the engine and turn on the AC to listen for compressor noise—if there's no sound, that's serious trouble. Then check if the pressure gauge really shows no reading. If confirmed, use soapy water to inspect pipe connections for bubbling leaks. Older cars are prone to this, especially in hot weather when low pressure becomes more noticeable, making driving uncomfortable and raising concerns about engine overheating. It's best to promptly visit a repair shop for a thorough inspection, leak repair, and refrigerant recharge—don't compromise safety to save a little money.
While driving, my car's AC suddenly stopped cooling, and I found the low-side pressure reading was zero, which is quite frustrating. Common causes include a refrigerant shortage or leaking seals—when pressure is too low, the system won't start, and the air won't get cold. A clogged expansion valve can also block refrigerant flow, resulting in no pressure reading. A friend once advised me to regularly inspect AC lines for oil stains or rust spots to prevent minor issues from escalating. You can use a simple pressure gauge to check the system, but before recharging refrigerant, make sure there are no other faults to avoid wasting money. Better take it to a professional shop soon—delaying will only make summer driving more miserable.
