The car ac should be as cold as the manufacturer design specifications according to the heat load, humidity, and other conditions of the vehicle at the time of the performance test. There is a relationship between Humidity, ambient air temperature, pressures and the type of refrigerant used in the auto a/c system that will ultimately dictate what the center duct air temperature in your car should be. In this chart of Relative humidity/ambient air temperature/pressure for r134a we can determine what should be the car ac temperature at the vents. If the vehicle is under these specific conditions of ambient outside air temperature and humidity and the Center Duct air temperature is not close to these values, there is a problem with the car a/c system that must be fixed.
Relative Humidity
Ambient Air Temp (F)
Max Gauge Pres Low Side (psi)
Max Gauge Pres High Side (psi)
Center Duct Air Temp (F)
40%
70
37
260
48
80
37
305
54
90
42
370
61
100
49
395
66
50%
70
37
275
52
80
39
320
57
90
46
375
64
100
55
430
72
60%
70
37
290
54
80
42
340
48
90
49
390
68
100
60
445
79
Temperature /Humidity/Pressure Relationships for R134a.
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This is a fast step by step guide on how to locate what is preventing the operation of the a/c system in your car. If the A/C in your car stopped cooling suddenly ,by knowing the a/c system pressure readings you can determine what component is not operating properly and replace it.
For the auto A/C system to operate we need the major air conditioning components to operate properly. When the a/c stop cooling suddenly we need to follow a logical diagnostic process to get to the cause of the a/c malfunction as fast and efficiently as possible. We’ll be looking to gather at least this useful information:
Exactly what is the concern.
When did the a/c fault happen ?
How often ?
Conditions of the vehicle at the time of the a/c fault.
Exactly what is the concern ? Is the auto ac not cooling enough or the cooling capacity has decreased. This category will lead us into a more specific area of the air conditioning system. Is the air coming out from the vents or there is no air at all blowing out from the a/c ducts ?
When did the A/C fault happen ? The approach will be different if the a/c fault only happens during the night or day and specific what part of the day or night. The ambient temperature will vary and the heat load on the car a/c system will be different.
How often ? Is the first time or is the problem repeating and how often? The more specific the information we get the easier the troubleshooting process will be.
Every time the auto A/C system is opened for a component replacement or any other type of service the service must be properly evacuated. Pulling a deep vacuum will ensure that all the ambient air that went inside the system while it was opened will be evaporated out of the system.
The negative impact of air contamination on the ac system will be noticed right away. Some of the signs of air contamination are noisy compressor operation and decreased overall auto ac performance. The air can’t be condensed inside the air conditioning condenser and only occupies the space of the refrigerant making the condenser less efficient and not allowing the process of de-superheat, condensation and subcooling that happens in the a/c condenser.
Auto A/C system Air contamination field test:
With 0% air contamination
High Side :165 PSI
Low Side: 32 PSI
Condenser temperature differential:38 Degrees
With 7.7 % Air Contamination
High Side : 200 PSI
Low Side: 31 PSI
Condenser temperature differential : 65 degrees
With 18.9% Air contamination
High Side:400 PSI
Low Side 45 PSI
Condenser temperature differential 102 Degrees
What damages could cause the air contamination in the car ac system.
Auto A/C system air contamination rises the overall pressure in the system. Higher than normal pressures will force the ac compressor. Higher pressures cause higher temperature that could change the oil viscosity and properties. A/C system air contamination will keep the condenser fan assembly operating at maximum capacity because of the inefficiencies of the condenser to change the refrigerant from vapor to liquid.
How to check for auto ac system air contamination ?
A refrigerant identifier can be used to quickly check for air contamination and refrigerant cross contamination.
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The amount of air that should come out from the vents will depend on the settings the driver has selected. In Automatic Temperature Control systems (ATC) the driver can choose a given temperature and have this temperature setting maintained by the a/c and heater control system.
This Fully automatic systems usually control most of the specific functions of mode operation, temperature control, blower speeds and heater temperature control. The system will automatically maintain the desired temperature and quantity of air for each mode and will route the airflow according to the need.
Why is my vent blowing weak air out.
One of these could be the reason why the vent is not blowing out enough air:
Fuses, fusible links, and wiring
Refrigerant charge and compressor operation
Coolant level
Heater core
Evaporator core
Blower motor control module
ECU
ECM
BCM
PCM
Ambient temperature sensor
Sun Load Sensor
Coolant temperature sensor.
The proper function of the ATC depends upon the electrical inputs of several sensors. The programming that enables the ECM to provide control of the system naturally tells the engine computer how to interpret these signals. The ambient temperature sensor is located just behind the grille outside the vehicle. Its job is to sense the outside air temperature and to adjust the ATC accordingly. In cold outside temperature the a/c compressor may be blocked to prevent ac compressor damage due to lack of proper internal oil lubrication.
The sun load sensor is mounted on top of the instrument panel. It senses the intensity of sunlight and adjusts the ATC to meet the demand.
Coolant temperature sensor. Its signal may come to the programmer directly, or be communicated to the programmer by the electronic control module (ECM).
How to unclog weak air flow from ac vents in a car
Poor air flow from vents in a vehicle could be related to any of the issues mentioned above. With the right tools and training the vehicle could be operating up to specifications in no time.
Do you need assistance with a Weak air flow from ac vents in car issue ?
We have ASE certified auto a/c mechanics near you. We can take care of any problem related to the a/c system that your vehicle may have. Call Us Today ! We service Miami-Dade County areas, Hialeah, Doral, Miami Lakes, Hialeah Gardens, Medley.
The reason could be the blend door actuator stuck in the cold setting position.
What is an automotive ac door actuator ?
The blend door actuator is a small electric motor. As you adjust the temperature up and down, the signals go through the actuator to complete the request, positioning the air door on the right position.
HOW DO I KNOW IF MY BLEND DOOR ACTUATOR IS BAD?
If an actuator binds inside the Hvac plenum, the control module will attempt to overcome the restriction several times before it shuts down the circuit. You will hear the ticking noise. If the binding clears on the next activation, the control module will perform a calibration and set a history DTC.
WHERE IS THE HEATER BLEND DOOR ACTUATOR LOCATED?
The a/c Blend door Actuator Motor is located on the Hvac Box underneath the dashboard. The exact location of the Actuator will depend on the Make, Model and Year of the vehicle serviced.
If you need assistance locating or replacing the blend door actuator in your vehicle, Contact us!
To check the auto a/c compressor compression ratio, note on paper the low and high side gauge readings and add atmospheric pressure to both readings. Divide the high side reading (with the atmospheric pressure added) by the low side reading (with the atmospheric pressure added).The result should be between 6.5:1 and 7.5:1. A compression ratio of 8:1 or higher may cause compressor failure. Learn More…
The A/C compressor is considered the heart of the refrigeration system. Compression ratio is the technical expression for pressure difference. Compression ratios are used to compare pumping conditions for a compressor and is an efficient way to evaluate the health of an air conditioning compressor.
If the A/C system operating pressures of your car gives you out of range values CALL US! We come to your place in Miami-Dade. Consider Auto A/C Repair LLC, always near your location!
The A/C system is designed to provide the passenger compartment with low temperature and low humidity air. During periods of high heat and humidity, an A/C system will be more effective in the Recirculation mode (MAX-A/C).
How cold should my AC be at the vent in my car?
A performance test is the best way to determine whether the system is performing up to design standards. This test also provides valuable clues as to the possible cause of trouble with the A/C system.
How do I check the temperature of my car AC?
Operate the heating-A/C system under the following conditions:
1-Engine at 1,000 rpm at operating temperature
Door and windows closed
2-Transmission in PARK or NEUTRAL with parking brake set (depending on transmission application)
3-A/C-heater controls set to recirculation mode (MAX A/C), full cool, panel mode, high blower and with A/C compressor engaged.
4-Insert a thermometer in the driver side center panel air outlet and operate the A/C system until the thermometer temperature stabilizes.
5-Compare the air temperature at the center panel outlet and the A/C compressor discharge pressure (high side) to the A/C Performance Temperature and Pressure chart.
