Is the refrigerant sight glass difficult to see?
Is it dark or clouded?
There could be several reasons.
First I'll start with the obvious.
What you actually see, may not be the glass. It may actually be the refrigerant.
I have seen refrigerant mixed with dirty or burnt refrigeration oil, appear very dark as it passes by.
How did the refrigerant become dirty?
It's usually indicates a recent compressor burn-out. The system was not cleaned properly.
Eventually the glass begins to accumulate a dirty film.
It becomes darker and darker until the view is simply a dull black.
What to do?
The obvious solution is to disassemble the glass (if possible) and wipe it clean. Or replace the entire component.
But more importantly, clean the refrigeration system!
You can imagine how dirty the entire refrigeration system is, if you can actually see the contaminates in the refrigerant.
How about a white or yellow film on the glass?
What causes that?
Chances are the filter drier is breaking down. The drier core is releasing a fine powder that coats the glass.
Time for a new drier.
Often, the glass becomes scoured.
What do I mean by scoured?
It appears scratched or pitted.
This is often caused by acid in the system from a past compressor burn-out.
Older sight glasses, with years of constant exposure to moving refrigerant, actually wear away.
Tiny glass particles begin to break off.
Once again, replace it.
See what I mean?
This little piece of glass tells tales!
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