i have a problem with this unit that give me low pressure alarm and my charge is ok and also my compressor is ok but i am not sure about signal that recieved to expansionto open it if any one helping me ,i will be thanks for him
Guessing you might have an electronic valve with a superheat controller. lets say its a sporlan for example. there is a sensor in the suction line, and both sensor and valve get wired back to controller somewhere. the controller needs to be looked at to see if sensor is reading correctly, and if it is set right. for many, you need a manual, and in some cases, a display module to troubleshoot issues. google the device or post it here, lots of guys know "how to deal with them".
You need to get some lit. on the machine or you are shooting in the dark. My typical experience is that the valve is getting a 0 - 10 VDC signal from a logic board that is getting a signal from a thermistor. Something could be wrong with any three of those components.
EEV OR SOMETIMES CALLED LEEV, are used on mini splits , vrv, s . from the literature you will get a resistance reading across the coil head , if that ohms ok check the output voltage off the board , mind you the connections are minute you will need minature or sub minature test leads , that wiil clarify the electrical side of an eev
Only use a very high quality DMM, and with a fresh battery or batteries, and very good condition test leads etc. These valves are typically 500 steps between 0 to 10 v's DC as mentioned. Tolerances of the sensors is very minute so a slightly oxidized connection will make radical changes in it's valve response etc.
However they are the future and are not going away that is for sure!