Bill Ball

As these tanks get somewhat low, they may not dispense liquid when inverted. Must be that the tap has a tube on it entending a bit into it (I haven't opened one to check). My Freon tank, originally 70 pounds, has 4 or 5 pounds left in it dispenses gas inverted or right side up.

Rob Edwards

Good point, Bill- this tank still weighs about 24 lbs, so still ~2/3 full.

Bill Ball

I've always thought of you as a lucky guy.

Gretch

So to be clear..... You can charge the system with the engine off, and can inverted, OR... the engine running and the can upright.

Can on low side valve.

Is this correct?

Why would ANYONE want to charge the system with the engine off and the AC not running?

inquiring minds want to know!!!!!!!!!

Speedtoys

If its evacuated, you can let the vacuum pull in the required weight of charge REALLY fast..and be done.

Your other assumptions are correct..never add liquid to a running system...its like pouring water into your intake while the engine is running.

Bill Ball

NOT QUITE RIGHT. You only do the inverted can method on the HIGH SIDE port unless your name is Randy and you are a lucky guy. The high side is were you expect liquid to be, after the compressor. Before the compressor (low side) is for gas (can upright), which the compressor can compress. I still do mostly low side charging (with the can upright in a bucket of hot water). I start with the engine off. The cans can push in about 50 PSI before it equilibrates. As the pressure approaches that, I start the motor, AC on, and the compressor sucks the rest in.

Speedtoys

<--was lucky too. Takin notes.

Rob Edwards

Actually, the fill hose connects to the high side. Right there in front of the condenser. Easy peasy. Everything's nice and cool, no burning your hands on the radiator hose trying to get to the low side connector, filling goes much faster (~90 seconds vs. 10 minutes of vapor via the low side while running the car), and at the end of the day, it doesn't matter how you get the refrigerant in, as long as you get the correct mass of refrigerant in there.

Gretch

Ditto.........


slinking away.........


Thanks Bill for saving my life and schit.......

dr bob

There's a lot of AC info scattered around in various threads. Sometimes I post stuff that assumes some level of basic knowledge of refrigeration service techniques, like where to push the refrigerant when charging. Obviously that's a poor assumption. AC is a system that demands extreme care and cleanliness to work correctly, and doesn't tolerate shortcutting too well. As many have discovered, mistakes can be very costly. I strongly recommend that folks buy or borrow a basic AC service manual, like Chilton's or Haynes, and study the way that systems work. There are plenty of examples of what to do and what to look for, far beyond what you might glean from our collective expertise in one or two questions and posts. These are available in paperback from Amazon for less than $10 for the basic stuff, and get more serious with hardback reference manuals for more money. Bottom line is that advice here is kind of like what you get in the WSM's, where there's an assumption that you have at least a basic education on the subject matter before you even ask the first car-specific question.

Randy V

This is what I'll do.

When starting the car, run both AC systems on high.

Last question is: Run in recirc mode or outside air mode - or doesn't matter either way?

Bill Ball

You could argue advantages for either way. Recirc mode with doors and windows closed could cause the compressor cycle off at some point and slow down getting to the full charge amount.

Randy V

Completed without problems.

Nice and cold now!

AO

I'll jump in on this too...

Which side would one evacuate/vacuum things down ideally?

I REALLY like the idea of fulling with liquid on the high side. That low-side port is a MAJOR PITA!

dr bob

Andrew-

FWIW, I plug both hoses into their respective ports, attach the yellow hose to the bottle, and plug the vacuum pump into the double-top-secret port where the pressure transducer for the fan normally sits. That way I can completely evacuate the whole charging manifold all the way to the bottle, no risk of air entrainment in incoming refrigerant stream. I know it's not the standard recommendation, but call it "cheating with a purpose". For those with pre-S4 cars, the pressure safety switch sits on a similar R12 port with Schraeder valve.

Related thoughts:
-- Cars converted to R-134a need both of these Schraeder valves replaced with updated versions, with HNBR seals intended for the synthetic compressor oils.

-- DO NOT remove the vacuum pump hose without verifying that the new valves will actually hold under vacuum. My vacuum pump has its own check-valve built into the last pump stage so no worries. Other pumps may not have that feature. If the Schraeder valve you are using does not seal under vacuum, it's probably better to use the center manifold hose and put the sensors back on.


And to the original question, it's a good idea to vacuum at both ports. You never know when one of the Schraeder valves in the charge ports will not open correctly. More than a few systems have been very quick to evacuate and seem to hold vacuum very well, only to find later that the depressor in the end of the hose didn't actually open the Schraeder valve.

Note also that the R12 charging hoses have a depressor in one end only; Putting that end of the hose on the manifold instead of the car will leave the valve closed. There's a small tubular seal in that end too, looks like a really short section of rubber vacuum hose. It's there to maintain the seal integrity while the hose is put on and taken off, while the flare seal isn't tight but the valve may be depressed. Both the valve depressor inserts and the rubber seal inserts are available as common replacement parts, and must be used together.