Car AC Compressors: Speed Control & Temperature Regulation

In summary, the compressor speed in a car air conditioner is controlled by monitoring the system's high-side pressure and switching the compressor on and off as needed. In electric air conditioners, the compressor is not directly driven by the engine and is commonly used in hybrid vehicles. The core differences between air conditioners and refrigerators lie in their working fluids and operating requirements. Temperature is controlled by moving vent doors inside the passenger compartment, not by the compressor. The velocity of the refrigerant fluid circulation may affect the rate of cooling, but the main factor is maintaining adequate high-side pressure.
  • #1
Charles123
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How is the compressor speed controlled in a car air conditioner, in compressors driven by engine moved belts? Is temperature controlled just by on/of of the solenoid clutch?
Electric air conditioner (automotive), not driven by (directly) by engine, is widely used today?
Another question, not related to car systems. What are the core differences between ac and refrigerators? Is the refrigerant type the main issue?
Thank you
regards
 
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  • #2
Charles123 said:
How is the compressor speed controlled in a car air conditioner, in compressors driven by engine moved belts? Is temperature controlled just by on/of of the solenoid clutch?

Yes, the compressor is switched on and off as needed by monitoring the system's high-side pressure.

Charles123 said:
Electric air conditioner (automotive), not driven by (directly) by engine, is widely used today?

There are some models out there that utilize them, mainly vehicles with engines that automatically turn off during stops such as hybrid vehicles.

Charles123 said:
Another question, not related to car systems. What are the core differences between ac and refrigerators? Is the refrigerant type the main issue?

Analytically they are basically the same. They use different working fluids due to different operating requirements.
 
  • #3
Thank you for your answer.
So in belt driven compressors their speed is not controlled, there is just an on/off switching as needed, doesn’t matter the engine rpm? The temperature is just controlled by this plus the mixture of air that passes through the evaporator and air that does not?
Related to refrigeration systems, their core dimensioning factors would be what? Compressor speed? Pipes diameter? Plus as you mentioned the refrigerant type…
Regards
 
  • #4
Charles123 said:
So in belt driven compressors their speed is not controlled, there is just an on/off switching as needed, doesn’t matter the engine rpm?

The minimum engine idle speed (RPM) is high enough to allow proper operation of the compressor. The 'click' you hear as a car is running with the A/C on is the compressor clutch engaging and disengaging to either build up pressure (the high side pressure Mech_Engineer spoke of) or stop building up pressure. Once this pressure reaches a low enough point, the compressor clutch is once again engaged.

Charles123 said:
The temperature is just controlled by this plus the mixture of air that passes through the evaporator and air that does not?

Temperature is controlled by moving vent doors inside the passenger compartment. Not the compressor.
 
  • #5
Thank you for your answer.
"The minimum engine idle speed (RPM) is high enough to allow proper operation of the compressor. The 'click' you hear as a car is running with the A/C on is the compressor clutch engaging and disengaging to either build up pressure (the high side pressure Mech_Engineer spoke of) or stop building up pressure. Once this pressure reaches a low enough point, the compressor clutch is once again engaged."
But the compressor keeps running at all times?
“Temperature is controlled by moving vent doors inside the passenger compartment. Not the compressor.”
But the velocity of the refrigerant fluid circulation doesn’t affect the rate of cooling, like in other AC systems?
Regards
 
  • #6
Charles123 said:
But the compressor keeps running at all times?
No. If the compressor clutch is not engaged, the compressor doesn't run. Only the pulley continues to be driven by the belt.
Charles123 said:
But the velocity of the refrigerant fluid circulation doesn’t affect the rate of cooling, like in other AC systems?
Regards
I'm not certain what effects the velocity of the refrigerant has on the rate of cooling. When there is an adequate amount of High Side pressure, cooling will take place. And once that pressure drops to a low enough amount, the compressor clutch is told to engage, and the compressor starts building High Side pressure again.
 
  • #7
"No. If the compressor clutch is not engaged, the compressor doesn't run. Only the pulley continues to be driven by the belt."
Of course...

"I'm not certain what effects the velocity of the refrigerant has on the rate of cooling. When there is an adequate amount of High Side pressure, cooling will take place. And once that pressure drops to a low enough amount, the compressor clutch is told to engage, and the compressor starts building High Side pressure again."
If the refrigerant is not circulating there will be no cooling...
 

1. How does the speed control of a car AC compressor work?

The speed control of a car AC compressor is typically controlled by the vehicle's engine. The compressor receives power from the engine through a belt and pulley system, and the speed of the compressor is regulated by the engine's RPM. As the engine speeds up, the compressor spins faster, increasing the flow of refrigerant through the system and ultimately cooling the car's interior.

2. Can the speed of a car AC compressor be adjusted manually?

In some cases, yes. Some vehicles may have a manual control knob or button that allows the driver to adjust the speed of the AC compressor. However, in most modern cars, the speed control is automated and adjusted by the engine's RPM.

3. How does the temperature of a car AC compressor affect its performance?

The temperature of a car AC compressor can greatly impact its performance. If the compressor gets too hot, it can overheat and potentially fail. This is why it is important to regularly check and maintain the AC system, as well as avoid placing extra strain on the compressor by running it at full blast for extended periods of time.

4. What role does the compressor play in regulating the temperature of a car's AC system?

The compressor is a crucial component in regulating the temperature of a car's AC system. As the compressor compresses the refrigerant, it causes a decrease in pressure and temperature. This cold, low-pressure refrigerant is then pumped through the AC system, absorbing heat from the air inside the car and cooling it before it is released back into the vehicle.

5. How can I tell if my car's AC compressor is malfunctioning?

There are a few signs that may indicate a malfunctioning AC compressor. These include loud or unusual noises coming from the compressor, warm air blowing from the vents when the AC is turned on, and visible leaks or damage to the compressor. If you suspect that your car's AC compressor is not functioning properly, it is best to have it checked by a professional mechanic.

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