What Causes the High Pressure Temperature in a Car's Air Conditioning System to Be Exceptionally High?
2 Answers
The reasons for the high pressure temperature in a car's air conditioning system may include: incomplete vacuuming during maintenance, leading to air entering the system and increasing the condensation pressure; the use of low-quality refrigerant; the condenser's electric fan not opening properly or insufficient fan speed; the condenser being blocked by debris and unable to dissipate heat effectively; or a slightly clogged expansion valve. To accurately diagnose high pressure in the car's air conditioning system, it's necessary to also check the low pressure. If both high and low pressure readings are excessively high, there are six possible causes: 1. Air in the system. The solution is to completely evacuate and recharge the refrigerant. 2. System blockage, often due to a clogged or malfunctioning expansion valve. The solution is to replace the expansion valve. 3. Excessive refrigerant. Symptoms include the exhaust port feeling hot to the touch and the suction port feeling warm. Normally, these areas should feel cool. The compressor may also produce liquid slugging sounds. The solution is to completely evacuate and recharge the refrigerant with the correct amount. 4. Poor condenser cooling. Symptoms include the section of the pipeline from the condenser outlet to the expansion valve inlet feeling hot to the touch, when it should normally feel warm. The solution is to clean the condenser and radiator grille of debris, and replace them if necessary. 5. Expansion valve failure. Symptoms include the low-pressure pipe having excessive condensation or frost. The solution is to check if the expansion valve is installed correctly and replace it if necessary. 6. Other faults, such as cooling fan failure, engine overheating, or excessive or insufficient refrigeration oil.
I used to run a repair shop and often encountered this issue. Car owners always complained that the AC was blowing hot air with unusually high pressure. The main reason is usually poor heat dissipation from the condenser. The cooling fins get completely clogged with dust and mud, the fan spins too slowly or gets stuck, and of course, the high-pressure pipe becomes scalding hot. Another common issue is overcharging the refrigerant, which forces the compressor to work excessively, causing temperatures to skyrocket. One customer's car had a condenser completely blocked by poplar fluff—when we removed it, the high-side temperature read over 90°C, but after cleaning, it immediately dropped to 50°C. I recommend cleaning the radiator every quarter, especially after long trips to remove dead bugs and debris. It's just like a computer heatsink—if it's clogged, it overheats.
