Hagen Brothers farms,Goodrich ND | Rich - 6/20/2009 08:03
I wouldn't say a vent thermometer is necessary Jon. I sit in the cab with everything opened up and the a.c. running full blast and go off of what it feels like to suit my taste.
Old R12 systems the rule of thumb was 100 psi over ambient temp on the high side. If it was 90 out then the high side when full would be 190.
Now it's nothing to get dang neart 300 psi into some of these systems.
You can make a.c. as perfect of a science as the mechanic on the sprayer was trying or you can do some pretty fast basic things and still have a cool a.c.
Watching air bubbles in the receiver dryer is a thing of the past. The system can be functioning perfect and still have air bubbles with 134A.
I don't care what people tell you or what my instructors tried telling me in school......A can of freon in a coffee can of hot water is going to speed up the filling process. Remember that lil trick.
Also, Alot of systems have a high pressure relief so if you get to much in it will blow off.
On a dry system with vacuum you can dump one can of freon in the high side as liquid. Otherwise always fill the system through the low pressure hose as gas.
Small hoses indicate high pressure (red) and larger hoses indicate low pressure (blue)
Hows that for a crash course?
Rich, I like the little $3 vent thermometer because it allows me to charge a converted R12 to R134a system by vent temp alone. I have had my best luck doing that. I add enough R 134a to get the system working, then with a vent thermometer in place, I add more R134a, a few OZ at a time until adding a bit more no longer lowers the vent temp. That seems to give the most cooling with the least high side pressure when I stop adding refrigerant at that point.
boy I agree on using warm water to boil off the refrigerant as vapor.
After blowing the reed valves out of a York compressor by slugging it with liquid refrigerant, I learned to charge vapor only when added at the compressor.
A 5 qt ice cream pail full of warm tap water contains enough heat to boil off enough R134a for the average recharge(3-5 cans) and your not gonna screw up the compressor.
And yep, the R12 sight guage is useless with R 134a. Synthetic Ester oil moves around in R134a in tiny globs that look exactly like the bubbles in an old R12 system. Ain't no way to eliminate them and they give a false indication of low refrigerant in a sight glass.
Seems like the new rule of thumb with R134a is that "normal" high side pressure is going to be 2---2-1/2 times ambient temp. |
Air conditioner crash corse
