What Causes High Pressure in Car Air Conditioning?

[SanRuth]

High pressure in car air conditioning may be caused by incomplete evacuation during maintenance, leading to air mixing into the system and increasing the condensation pressure. Other causes include the use of inferior refrigerant, the condenser's electric fan not opening properly or having insufficient airflow, the condenser being blocked by foreign objects and unable to dissipate heat normally, or slight blockage of the expansion valve. To better diagnose high pressure in car air conditioning, it's also necessary to check the low pressure. If the high pressure reading is too high and the low pressure reading is too low, there are two possible causes: first, the expansion valve may be blocked due to the failure of the receiver-drier, allowing contaminants to enter and clog the valve; second, the power element may have failed, often because the temperature-sensing bulb has lost its charge, keeping the valve in a constantly closed state. The solution is to replace the expansion valve and the receiver-drier.

[OJosephine]

I found that when the car's air conditioning high pressure is too high, it's usually due to poor heat dissipation; for example, if the condenser is clogged with dirt or the fan isn't working, the heat can't be expelled, leading to increased pressure. Also, adding too much refrigerant can cause the system to be overfilled with liquid, causing pressure to spike. If the expansion valve gets stuck and doesn't open, refrigerant flow is blocked, which can also lead to high pressure. Additionally, air or debris entering the system and causing blockages can have the same effect. It's recommended to regularly check the condenser for cleaning and the fan's condition, and avoid overfilling the refrigerant. If high pressure isn't resolved, the system can be damaged or even burst pipes, causing more trouble during driving. Pay extra attention during hot weather—if the AC isn't cooling properly or making strange noises, these are warning signs. Get it fixed early to avoid costly repairs later.