A/C SIGHT GLASS DIAGNOSIS.
A sight glass is a transparent glass tube or
window installed in a tank or boiler system that allows an observer to view
what is happening inside the system.
The refrigerant sight glass is normally located anywhere
liquid flow exists and anywhere it can serve a purpose. When it is installed
just prior to the expansion device, the technician can be assured that a solid
column of liquid is reaching the device. When it is installed at the condensing
unit, it can help with troubleshooting.
Sight glasses come in two basic styles: plain and with a
moisture indicator. The plain sight glass is used to observe the refrigerant as
it moves along the line. The sight glass with a moisture indicator can tell
what the moisture content is in the system. It has a small element in it that
changes color when moisture is present.
What you see in the sight glass can help you diagnose system
malfunctions. It is strongly
suggested that you do not use the sight glass as the only means of diagnosis.
Also, do not use the sight glass to diagnose R134a systems.
If the sight glass is clear, one of three conditions can exist:
the system is completely empty, the system is full, or the system is overcharged.
If there is foam, the charge is low, but if there are only a couple of bubbles,
it is probably Ok. few bubbles when the compressor cycles on is normal. Oil
streaks in the sight glass usually indicate a low charge and that the
compressor is pumping oil from its sump. If the sight glass is cloudy, the desiccant
bag has probably burst.
If an R134a
system has a sight glass, do not use it or try to perform diagnosis, as it is
normal to observe bubbles in this type of system.
READING A SIGHT GLASS
SIGHT GLASS CLEAR
System empties (No refrigerant)
SIGHT GLASS, FOAM, BUBBLES OR MIST.
low on refrigerant
contaminated with air
SIGHT GLASS STREAKED
may be low on refrigerant
may streak as oil circulates