One of the main problems with AC is that it blows hot air or air is not cool enough. This problem can be caused by various reasons: there could be a problem with wires that are not allowing the compressor to turn on, AC could be low on refrigerant, the internal problem with the system, control panel not working properly. Most of the time the problem is with refrigerants.
If your AC is not working properly, it is a good idea to hook your AC’s compressor to a pressure gauge to find out what is causing this issue.
Pressure in the AC system and temperature have a relationship between them. A chart showing temperature can be used to compare the pressure of the refrigerant at the given temperature. Since there is no way to determine how much refrigerant is left in the system without opening and measuring it, we will use pressure and compare it to a pressure-temperature chart?
- Hook up the pressure gauge to the system.
- Record the pressure, both high and low, should be equal.
- Measure the temperature.
- Is the pressure matching the pressure-temperature chart.
- The temperature should match the chart, which means the refrigerant level is good.
- If the pressure level and temperature do not match, that means the refrigerant level is low. The system probably is leaking
- If the pressure gauge is showing zero, it means that the system has a major leak.
- If the pressure level is higher than what it should have been, according to the charts, it means that there is air in the system or the system is overcharged.
To check the pressure of the system. First of all, start the engine, then turn on the AC, check if the compressor is running.
- When the AC was started, you should have heard a click sound, check if the centre hub turning or not.
- Check the pressure gauge—are they working properly? Is the low side going down and the high side going up?
- After some time has passed, raise the RPM levels to 1500.
- An AC properly working AC system should show readings somewhere between 200-250psi on the high side and 25-30psi on the low side. The pressure should go up and down accordingly to the temperature.
The high and low sides are showing the same pressure
No change in the high and low side pressure is still equal.
- Check if the temperature clutch is engaged.
- Try to turn the centre hub—if it is turning, that means the compressor is not working.
- Shut off the engine and try to rotate the centre hub by hand, is there any resistance?
The compressor may be faulty.
The pressure gauge is showing higher pressure on both high and low sides, it could mean that there is a problem with the airflow condenser.
- Check if the cooling fan working.
- Check if the condenser fan is slightly bent or dirty.
- Check if there is a blockage inside the condenser fan.
Lower high and lower low pressure indicates that there could be a problem with pressure building inside the system or too much heat is being removed from the condenser.
To check it place a fender cover on the condenser while the engine and AC are running and then check the temperature.
- If the pressure is still not going up, the compressor may be worn out.
- If the cooling fan is running non-stop. A pressure switch or sensor is broken and is not working properly.
Lower Low Side and Higher High Side
If reading is showing lower on the low side and higher on the high side, it means that the orifice tube is being blocked or closed by something. Try feeling the lines is there a drop in temperature in the orifice tube.
Higher Low Side and Lower High Side
It means that the amount of refrigerant flowing into the evaporator is too much to handle.
- TXV is open or the thermal bulb is at fault, it is not sensing the temperature properly.
- The orifice tube has a large opening somewhere or the o-ring sealing outside the orifice tube is not sealed enough.
Below is a list of readings that characterises the problems behind a faulty AC
- High-250 PSI low-30 PSI- You have air leaking somewhere in the system. Go to a mechanic and tell them about this problem. Air leaking is one of the most common issues for car AC to not work properly. It happens because of wear and tear when the car begins to age.
- High-250 PSI low-50 PSI- Not able to properly cool down the condenser is overcharged or overheating. The reason behind the condenser not cooling down could be that the condenser is being blocked by some object. The condenser takes refrigerant from gaseous state to liquid state by removing the heat, if the condenser is being blocked by something the AC will not blow cool air. If you are facing this problem with your car consider replacing it or try to fix it with the help of a professional mechanic.
- High-220 PSI low-80 PSI- This happens because the expansion valve is too wide( this is not a problem if your car has an orifice tube). Also, another reason that could be causing this problem is that your AC system has too much refrigerant in it. Don’t try to readjust the valve as it is only a temporary solution, you should consider replacing the valve.
- High-200 PSI low-70 PSI- This reading is shown when there is a blockage in the system and it is interfering with the airflow in the system, resulting in AC not being able to cool the car properly.
- High-160 PSI low-10 PSI- This reading is shown when the expansion valve is clogged, the evaporator is frozen, low pressure in piping. To know the source of the problem, check these areas: expansion valve, piping, evaporator by yourself or take the help of a professional mechanic. If the valve is clogged, it means that there are not enough refrigerants it causes the system to overheat and cause other problems. If this is the case you will need to change the clogged valve.
- High-150 PSI low-30 PSI- This reading is shown when there is water in the system. It is perfectly normal and a good sign if you see water draining out of the car. The problem starts when you don’t see the water draining outside your car instead, you are met with water strains inside your car. It simply means that there is water inside your system which is not able to drain out due to many reasons. It is recommended that you book an appointment with your mechanic to fix this problem because it can seriously damage your car’s AC system.
- High-150 PSI low->10 PSI- This reading is shown when the expansion valve is being stuck open or there is a leakage somewhere. If the expansion valve is stuck open, it would result in overheating of the compressor and it allows too much refrigerant to pass through the system.
- High-125 PSI low-30 PSI- This reading is shown when there is too much oil present in the compressor or it is not receiving sufficient power. If there is too much oil in your AC’s compressor, it can coat the inner walls of the evaporator and the condenser coils, this will reduce the effectiveness of the AC to disperse heat properly and you will feel like that the AC is not cooling enough. To drain the excess oil which is present in the compressor, it is advisable to see a mechanic.
- High-100 PSI low-100 PSI- This reading is shown when the compressor is not receiving enough power or is working with a burnt coil. This happens because of the poor maintenance of the system or by acid reaction inside the system, which results in a burnt coil. To fix this issue, you will need to replace the burnt coil with a new coil and after replacing it, your AC should work fine.
- 50 PSI / 50 PSI– This reading is shown when the clutch is not engaging. If the clutch is not engaging the AC will not blow out cool air. The clutch can get damaged due to some electrical problems in the car. To fix this problem it is advisable to visit a mechanic to fix this issue.
There are a lot of reasons your car’s AC is not working properly, you can easily check what is the main cause of this problem by using a pressure gauge and a temperature chart to check what could be the underlying problem, which is causing your AC to not work efficiently or not blowing out cool air. This article only provides you with the basic problem that can cause your car’s AC to malfunction. It is recommended not to open any part or try to fix anything by yourself, consider consulting a professional mechanic they know better than you. There are a lot of problems that can be determined by just comparing the pressure and the temperature, but there are also other reasons that can also interfere with the proper working of your AC. If the pressure gauge and temperature chart are showing the proper results but the air is still not cool enough, consider booking an appointment with your mechanic and get your car checked to find out what is causing this problem.