Reasons for High Low Pressure and Normal High Pressure in Car Air Conditioning

[OKing]

Under normal conditions, when the compressor operates at 1500-2000 rpm, the high pressure should be around 1.5-2.0 MPa, while the low pressure should be around 0.15-0.35 MPa. The reasons and solutions for high low pressure and normal high pressure in car air conditioning are as follows: 1. When the car air conditioning exhibits low low pressure and normal high pressure, it is highly likely due to a malfunction or damage of the air conditioning expansion valve. 2. Solution: The solution for high low pressure and normal high pressure in car air conditioning is very simple. Just remove the air conditioning expansion valve and check if it is functioning properly. If it is found to be faulty or damaged, simply replace it.

[LeRiver]

Last time my car's A/C was blowing cold air slowly, the experienced mechanic said the low-pressure pipe felt extremely cold and even frosted over, while the high pressure was normal. The main issue was a stuck expansion valve, causing too much refrigerant to spray into the evaporator. Alternatively, it could be worn compressor pistons that only draw in gas without increasing pressure. Another possibility is air or moisture entering during previous repairs, causing erratic low-pressure readings. The most effective solution is to connect pressure gauges to both high and low-pressure ports for dynamic testing, then clean or replace the expansion valve. If the compressor is faulty, repairing it would be costly, so replacement is better. Remember to completely evacuate the system before refilling with refrigerant, or all efforts will be in vain.

[LaElena]

I've encountered situations where the low pressure in the AC system spikes. A loose compressor belt slipping can cause insufficient suction, preventing the low pressure from dropping naturally. A clogged dryer bottle can also obstruct refrigerant flow, causing falsely high low pressure. Sometimes overcharging the refrigerant or mixing different types can throw the pressure readings off. The most troublesome issue is when the AC control module sends wrong signals, failing to properly close valves. I recommend first releasing some refrigerant to observe pressure changes, then checking for loose connections at the compressor clutch and sensor wiring plugs.

[StAlex]

Low pressure is high while high pressure is normal – focus on the refrigeration cycle system. A failed expansion valve can cause excessive liquid refrigerant to flood the low-pressure side, increasing the compressor's suction resistance. A faulty temperature sensor may keep the expansion valve fully open. If the evaporator coil's fins are clogged with dust or leaves, heat exchange efficiency drops, and low pressure will also rise. Incomplete vacuuming leaving residual moisture can cause ice blockages in the pipes. You can remove the expansion valve to check if the filter screen has metal debris, which is a sign of compressor wear.