MS121 – Tester for electromagnetic clutches and control valves

How to check the electromagnetic clutch of the air conditioning compressor

Most of the air conditioning compressors that are produced for the automotive industry have an electromagnetic clutch of inclusion. And one of the most frequent faults is an open in the power supply circuit, or an inter-turn fault, causing the compressor to stop turning on.

It is quite easy to check the coupling: for this, it is necessary to connect a car battery using two wires with a cross section of at least 1 mm2. As a result, the clutch will either work or not, which will make it possible to judge its condition. The problem with verification can be the fact that most couplings have a limiting diode. If the connection polarity is incorrectly selected, the diode will burn out. When using the MS121 compressor control valve tester, the possibility of damaging the diode is excluded, which simplifies the repair process or at all helps to avoid it.

Checking the air conditioner compressor control valve, besides ac compressor test bench,  in fact, is very similar to checking the electromagnetic clutch or compressor valve leak testing . The control valve also operates on the principle of an electromagnet, acting on the angle of inclination of the swash plate and, thus, changing the performance of the compressor. However, unlike the coupling, the valve mechanism has intermediate positions. The degree of valve opening is controlled by a PWM signal of a certain frequency and a varying duty cycle. Thus, it is possible to check the operability of the control (control) valve by changing the duty ratio of the signal applied to it directly on the vehicle. Changing the pressure of the HP main line in accordance with the change in the control signal and will indicate the serviceability of the valve.

This method is convenient in that there is no need to remove the refrigerant from the car air-conditioning system, since the filling operation itself is quite expensive.