Community Forums

hypoxia · 06-08-2020, 05:07 AM

Are there bubbles in the dryer sight glass when the A/C is running? It is usually painted over so you scrape the paint off to see the glass.

Isaac-1 · 06-08-2020, 07:41 AM

The sight glass method does not work well on R134a as it can still have bubbles when at proper charge level unlike the old R12 systems, so using this method can often lead to over charging.

Xmcdog · 06-08-2020, 07:57 AM

Quote:

Originally Posted by Isaac-1

The sight glass method does not work well on R134a as it can still have bubbles when at proper charge level unlike the old R12 systems, so using this method can often lead to over charging.

Only if you have a condensing problem.
Sight glass charging works very well as long as the system is working as designed. A clean condenser is essential.

Xmcdog · 06-08-2020, 08:27 AM

Ok just for the record.
The pressures in a refrigeration system will change with the ambient temp. The discharge or high side at 95f should be about 190-200 PSIG. That is the outside temp.

Now to determine what the pressure should be get a pressure temperature chart for R-134A. Check your ambient temp and add 30f. So 95f becomes 125f. This is known as the condensing temp. Apply this to your chart and you get 190-200 PSIG. This is the condensing pressure.

There will be differences as this applies to a new system but any major differences indicate a problem. Eg a discharge pressure of say 300 PSIG suggests a dirty condenser or faulty fan.

On a farm tractor I have seen 600 PSIG. Yes the HP cut out was faulty. I blew out the condenser with compressed air. Very little difference. Washed it out with a garden hose and it all came back to normal. So read and understand your gauges.
Incidentally there are PT "charts" on your gauges.

PT charts are available online.
Good luck

Hoss7 · 06-09-2020, 11:26 AM

I will give both the condenser and evaporator coils a good wash and will wrap the expansion valve with new prestite cork tape, and will check to see if there's any noticeable drop in vent temperatures! Thanks everyone for everyone's knowledge and input, it's extremely appreciated!