Aircon Problem-OFW from KSA

[burjegol]

the fact that the subject vehicle is a 2006 chevrolet trailblazer, the refrigerant must be R134a and not R12; also, the fact that it is a chevrolet, it must be using an orifice tube; the fact that it is using an orifice tube, it must be using an accumulator/dryer and not a receiver/dryer- if there was a sight glass, the sight glass will always be cloudy since R134a appears cloudy and the sight glass (if equipped) is on the suction (low) side of the refrigeration circuit. the orifice tube may either be variable orifice tube valve (VOV) or a fixed orifice tube (FOV). the low side pressure varies between 27 psig to 35 psig. the outlet temperature is always advisable to be at 27 psig (32*F or 0*C). it should not freeze at this freezing pressure and temperature since warm cabin air and the cooling loads prevents this from happening and the pressure switch disengages the compressor clutch whenever the pressure goes down below 27 psig or the target temperature had been reached and cycles on and off. the discharge side varies with airflow across the condenser and the ambient temperature. the high side must be at least twice the static pressure of the refrigerant in the system at rest.

got to clear somethings about the facts you have stated.

1. could you elaborate what you mean by an accumulator/dryer and receiver/dryer? In my 30 years as an practicing HVAC engineer, i haven't heard this terminology. an accumulator is a big different from a dryer and from a liquid receiver.

2. Likewise sight glass is usually installed in the liquid side to monitor the refrigerant state. I have encountered a sight glass which is connected to the suction side but it was to monitor the oil return to the compressor. The vision of the sight glass in the suction side as you mentioned will be cloudy, Of course as you are viewing the vapor state of the refrigerant. since it is colorless, the probable medium you are seeing the oil entrained in the refrigerant. If the sight glass is installed in the liquid line, you will view a clear sight glass when refrigerant quantity is correct, in accordance to its operating pressure.

3. fixed orifice and variable orifice? what controls the variable orifice to open and close to regulate the flow of refrigerant? Or you just simply means capillary expansion device (fixed orifice) or thermostatic expansion valve (variable orifice) ?

4. the low side varies from 27 to 35 psig, at what rpm of the engine? and the setting of the low pressure switch to open at 27 psig is usually utilised in R-22 system. We are discussing about R-134 system.