How do you know if your car AC is working?

TEMPERATURE REFRIGERANT TEMPERATURE REFRIGERANT REFRIGERANT  
°F 12 22 134a 502 404A 410A °F 12 22 134a 502 404A 410A °F 12 22 134a 502 404A 410A
-60 19.0 12.0 7.2 6.6 0.3 12 15.8 34.7 13.2 43.2 46.2 65.3 42 38.8 71.4 37.0 83.8 89.7 122.9
-55 17.3 9.2 3.8 3.1 2.6 13 16.4 35.7 13.8 44.3 47.4 66.8 43 39.8 73.0 38.0 85.4 91.5 125.2
-50 15.4 6.2 0.2 0.8 5.0 14 17.1 36.7 14.4 45.4 48.6 68.4 44 40.7 74.5 39.0 87.0 93.3 127.6
-45 13.3 2.7 1.9 2.5 7.8 15 17.7 37.7 15.1 46.5 49.8 70.0 45 41.7 76.0 40.1 88.7 95.1 130.0
-40 11.0 0.5 14.7 4.1 4.8 9.8 16 18.4 38.7 15.7 47.7 51.0 71.6 46 42.6 77.6 41.1 90.4 97.0 132.4
-35 8.4 2.6 12.4 6.5 7.4 14.2 17 19.0 39.8 16.4 48.8 52.3 73.2 47 43.6 79.2 42.2 92.1 98.8 134.9
-30 5.5 4.9 9.7 9.2 10.2 17.9 18 19.7 40.8 17.1 50.0 53.5 75.0 48 44.6 80.8 43.3 93.9 100.7 136.4
-25 2.3 7.4 6.8 12.1 13.3 21.9 19 20.4 41.9 17.7 51.2 54.8 76.7 49 45.7 82.4 44.4 95.6 102.6 139.9
-20 0.6 10.1 3.6 15.3 16.7 26.4 20 21.0 43.0 18.4 52.4 56.1 78.4 50 46.7 84.0 45.5 97.4 104.5 142.5
-18 1.3 11.3 2.2 16.7 18.2 28.2 21 21.7 44.1 19.2 53.7 57.4 80.1 55 52.0 92.6 51.3 106.6 114.6 156.0
-16 2.0 12.5 0.7 18.1 19.6 30.2 22 22.4 45.3 19.9 54.9 58.8 81.9 60 57.7 101.6 57.3 116.4 125.2 170.0
-14 2.8 13.8 0.3 19.5 21.1 32.2 23 23.2 46.4 20.6 56.2 60.1 83.7 65 63.8 111.2 64.1 126.7 136.5 185.0
-12 3.6 15.1 1.2 21.0 22.7 34.3 24 23.9 47.6 21.4 57.5 61.5 85.5 70 70.2 121.4 71.2 137.6 148.5 200.8
-10 4.5 16.5 2.0 22.6 24.3 36.4 25 24.6 48.8 22.0 58.8 62.9 87.3 75 77.0 132.2 78.7 149.1 161.1 217.6
-8 5.4 17.9 2.8 24.2 26.0 38.7 26 25.4 49.9 22.9 60.1 64.3 90.2 80 84.2 143.6 86.8 161.2 174.5 235.4
-6 6.3 19.3 3.7 25.8 27.8 40.9 27 26.1 51.2 23.7 61.5 65.8 91.1 85 91.8 155.7 95.3 174.0 188.6 254.2
-4 7.2 20.8 4.6 27.5 30.0 42.3 28 26.9 52.4 24.5 62.8 67.2 93.0 90 99.8 168.4 104.4 187.4 203.5 274.1
-2 8.2 22.4 5.5 29.3 31.4 45.8 29 27.7 53.6 25.3 64.2 68.7 95.0 95 108.2 181.8 114.0 201.4 219.2 295.0
0 9.2 24.0 6.5 31.1 33.3 48.3 30 28.4 54.9 26.1 65.6 70.2 97.0 100 117.2 195.9 124.2 216.2 235.7 317.1
1 9.7 24.8 7.0 32.0 34.3 49.6 31 29.2 56.2 26.9 67.0 71.7 99.0 105 126.6 210.8 135.0 231.7 253.1 340.3
2 10.2 25.6 7.5 32.9 35.3 50.9 32 30.1 57.5 27.8 68.4 73.2 101.0 110 136.4 226.4 146.4 247.9 271.4 364.8
3 10.7 26.4 8.0 33.9 36.4 52.3 33 30.9 58.8 28.7 69.9 74.8 103.1 115 146.8 242.7 158.5 264.9 290.6 390.5
4 11.2 27.3 8.6 34.9 37.4 53.6 34 31.7 60.1 29.5 71.3 76.4 105.1 120 157.6 259.9 171.2 282.7 310.7 417.4
5 11.8 28.2 9.1 35.8 38.4 55.0 35 32.6 61.5 30.4 72.8 78.0 107.3 125 169.1 277.9 184.6 301.4 331.8 445.8
6 12.3 29.1 9.7 36.8 39.5 56.4 36 33.4 62.8 31.3 74.3 79.6 108.4 130 181.0 296.8 198.7 320.8 354.0 475.4
7 12.9 30.0 10.2 37.9 40.6 57.8 37 34.3 64.2 32.2 75.8 81.2 111.6 135 193.5 316.6 213.5 341.2 377.1 506.5
8 13.5 30.9 10.8 38.9 41.7 59.3 38 35.2 65.6 33.2 77.4 82.9 113.8 140 206.6 337.2 229.1 362.6 401.4 539.1
9 14.0 31.8 11.4 39.9 42.8 60.7 39 36.1 67.1 34.1 79.0 84.6 116.0 145 220.3 358.9 245.5 385.9 426.8 573.2
10 14.6 32.8 11.9 41.0 43.9 62.2 40 37.0 68.5 35.1 80.5 86.3 118.3 150 234.6 381.5 262.7 408.4 453.3 608.9
11 15.2 33.7 12.5 42.1 45.0 63.7 41 37.9 70.0 36.0 82.1 88.0 120.5 155 249.5 405.1 280.7 432.9 479.8 616.2

VACUUM (in. Hg)-RED FIGURES

GAUGE PRESSURE (psig)-BOLD FIGURES

How do you know if your car AC is working?

The temperature/pressure relationship correlates the vapor pressure and the boiling point of water and is the basis for controlling a system’s temperatures. So if we are able to control the pressures in refrigeration or air-conditioning system, we will be able to control the temperatures that the system will maintain. Whenever the pressure is increased, the boiling point increases, and whenever the pressure is reduced, the boiling point is reduced.

How does the air conditioning in my car work?

To explore how a real refrigeration system works, we will use refrigerant R-134a in the following example:

Find 40 °F in the left column of the chart read to the right, and notice that the gauge reading is 35.1 psig for R-134a.

What does this mean in usable terms?

It means that when R-134a liquid is at a vapor pressure of 35.1 psig, it will boil at a temperature of 40 °F.When air is passed over the evaporator coil; it will cool down your car at about that temperature.

The pressure and temperature of a refrigerant will correspond when both liquid and vapor are present fewer than two conditions:

  1. When the change of state (boiling or condensing) is occurring, and
  2. When the refrigerant is at equilibrium (i.e., no heat is added or removed).

In both conditions 1 and 2, the refrigerant is said to be saturated. When a refrigerant is saturated, both liquid and vapor can exist simultaneously. When they do, both the liquid and the vapor will have the same saturation temperature. The saturation temperature depends on the pressure of the liquid/vapor mixture, called the saturation pressure. The higher the pressure, the higher the saturation temperature of the liquid and vapor mixture. The lower the pressure, the lower the saturation temperature.

*Note: The same temperature for the liquid and vapor is not true of some of the newer blended refrigerants that have a temperature glide.

How to Diagnose Your Car’s Air Conditioning System ?

 

Tools and safety

When performing any air conditioning system service you must have the proper tools – and exercise caution when using them.

Tools Needed

manifold gauge set for taking ac system readings

  1. Air conditioning manifold gauge set
  2. Gloves
  3. Refrigerant
  4. Safety Glasses

Warning

Never add anything but the recommended refrigerant to the AC system.

Always wear safety glasses when servicing any pressurized system.

Never install the gauges with the system running.

By looking at the manifold gauge set and comparing with the pressure/temperature chart you’ll know how is the air conditioning in your car performing. For OEM specifications  click here.

Summary
How do you know if your car AC is working properly ?
Article Name
How do you know if your car AC is working properly ?
Description
By looking at the manifold gauge set and comparing with the pressure/temperature chart you’ll know how is the air conditioning in your car performing.
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Publisher Name
Auto A/C Repair LLC.
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