The test bench MS111 is intended to diagnose automotive air conditioning compressors in 80% operational conditions and as a consequence, it can be used both by as manufacturers of AC compressors and remanufacturers.
The test bench was invented on the basis of the highest requirements of the latest service centers on AC compressor reconditioning. The development of the equipment lasted 3 years, during them 5 modifications were made, which differed in either the internal components and the principle of testing.
We stood for three main function while elaborating the test bench: testing of the compressor endurance, run after repair, diagnostics of performance of the clutch and/or valve for a long period of time.
One of the modifications of our test benches was designed to determine the compressor performance and operated on dry compressed air, though, the disadvantage of this testing device was that the testing procedure lasted no longer than 1-2 minutes. Thus, we did not have an opportunity to test the compressor performance or run it after replacing the internal parts, these factors made its restoration impossible.
For the period of use of different versions of the test benches, after collecting a sufficient amount of information, it was decided to select the option with the unit operation conditions of maximum similarity to real ones, that is, the equipment were supposed to simulate an automotive air conditioning system.
Electronic sensors were selected as measuring tools. Their advantage over analogue ones is obvious: high accuracy, calibration possibility, synchronization of additional functions of the test bench to the signals of the sensors without using additional devices, as well as the ability to save testing results for further use.
An industrial computer was chosen as a device that processes the signals from the sensors, output information and controls the test bench functions.
Besides, use of the computer with specially developed software extends the equipment opportunities, allows to diagnose units in automatic mode (this function is under development), assess condition of units on the basis of sensor data, save diagnostic results, print them out, etc.
The table below shows some types of failures of AC compressors which can be easily identified with the help of this test bench.
Compressor failure | Detection of failure |
Electromagnetic clutch failure: open, short-circuit. | The status information is displayed on the computer screen after the clutch and/or valve is activated. |
Electromagnetic valve failure: open, short-circuit. | |
The clutch failure: increased clearance on the clamping plate. | The clutch does not work when switching on or the clamping plate slips during the testing. |
The pulley bearing noise. | Sounds as thump from the compressor. |
Noise, knock, sticking of the piston compressor. | Occurs at minimum and/or medium revolutions. |
Tightness, ability to retain vacuum. | Determined after connecting the compressor to the test bench by pressing the air pumping button. Vacuum should stay at one level. |
The compressor mechanical valve operation check. | Determined on the test bench in the mode of minimum load at medium speed. The LP pressure should not fall below the factory set level (most often 1.4 - 1.6 bar) and should not be above 2.8 bar with a maximum compressor load at 1500 rpm. |
The compressor electromagnetic valve operation check. | Determined on the test bench under all diagnostic modes. By increasing the valve PWM, the LP pressure should fall, decreasing the valve PWM, LP pressure should increase. |
To control the electromagnetic clutch and/or electromagnetic valve of AC compressor, such features as presence or absence of a diode in the electrical circuit were taken into account. A specialized switching mode was developed: to detect a diode, automatically determine the correct polarity of the power supply connection, detect the short or open coil. The data received after switching on is displayed on the screen.
The test bench also implies diagnostics of the compressor operation on the R1234YF refrigerant, while the diagnostics itself is possible with the R134a refrigerant using a special oil intended for work with both types of refrigerant.
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