How to Read an Automotive Air Conditioning Gauge?
2 Answers
There are two gauges for automotive air conditioning systems: the red one is the high-pressure gauge, and the blue one is the low-pressure gauge. The units on the gauges may be in bar and kilopascal (kPa), or pounds per square inch (psi). The conversion formula is: 1 bar = 100 kPa = 14.5 psi. Here are specific details about automotive air conditioning gauges: 1. Insufficient Refrigerant: When the automotive air conditioning pressure gauge shows low pressure on both the low and high sides, it indicates insufficient refrigerant, which is a common issue. Older vehicles may experience refrigerant leakage. After inspection, the problem can be resolved by simply recharging the refrigerant. 2. Expansion Valve Malfunction: When the automotive air conditioning pressure gauge shows high pressure on both the low and high sides, it indicates a stuck-open expansion valve. Poor cooling performance with both low and high pressures elevated suggests the expansion valve may be stuck open, allowing air into the refrigeration system and mixing high and low pressures, resulting in reduced cooling efficiency. Replacing the expansion valve can resolve this issue.
I usually repair my car myself and enjoy DIY air conditioning inspections. When checking the air conditioning gauges, the main focus is on the high and low pressure values. Car air conditioning systems typically have high-pressure and low-pressure gauge ports. After starting the engine and turning on the AC, the high pressure should normally be between 150 to 250 psi, while the low pressure should be in the 30 to 45 psi range. If the gauge reading is too low, such as below 30 psi, it might indicate insufficient refrigerant or a leak. If it's too high, exceeding 250 psi, there could be a blockage in the system or an overcharge of refrigerant. Once during summer, my car's AC wasn't cooling properly. After testing, I found the low pressure was only 20 psi, so I quickly added refrigerant to fix the issue. I recommend checking the system once a year before summer starts to avoid breakdowns on the road and wasted fuel costs. Such simple maintenance can save a lot on repair expenses.
