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Upside down 30lb disposable tank question

Notsobright on Fri September 04, 2015 1:50 PM User is offline

Year: 2005
Make: Chrysler
Model: Town & Country
Refrigerant Type: 134a

General question: I have use of Mastercool electronic scale which specifically states "place disposable tank upside down" I understand that after deep vacuum of system and with engine off, system can be filled with liquid (upside down tank) on high side. After reading all the warnings about slugging compressor, despite knowing this should not be a problem with vacuumed system with engine off, I still would like to know if there is any problem filling a vacuumed system with 30lb disposble tank right side up, on low side with engine running? Aside from the fact that it would take longer, is it ok to do it this way? thanks,

GM Tech on Fri September 04, 2015 2:20 PM User is offline

Sucking in gas is okay on low side- but will take a long time..

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Fri September 04, 2015 3:00 PM User is offline

It takes a long time, during that time you are running the compressor without good oil flow. Better to charge liquid with the engine off. If that doesn't get the full charge in, start compressor and finish as gas.

Notsobright on Fri September 04, 2015 3:43 PM User is offline

So you (mk378) would recommend charging evacuated system with disposable tank upside down, engine off, to high pressure side. and then if prescribed weight not reached, shut off red valve, turn tank right side up, start car, open blue manifold valve to finish charging. Correct??

mk378 on Fri September 04, 2015 4:58 PM User is offline

Yes though I would leave the tank upside down and just open the blue valve partway, This keeps the scale zeroed, if you move the tank it will likely read a different weight since the weight of the hose is in a different place. When the low side gauge jumps up that confirms you are putting refrigerant in. Do not open the valve much past that point with the compressor running and you will be fine about not slugging liquid in. Of course never open the high side valve with the engine running.

Notsobright on Fri September 04, 2015 5:35 PM User is offline

Great. Thank you very much.

GM Tech on Fri September 04, 2015 6:34 PM User is offline

And when you have "weighed in" the entire charge- shut off tank valve- and shut off high side valve at the a/c port on the car and open both red and blue (high and low side) valves on your gage set- this will allow most all liquid in your gage set hoses to be sucked in the low side- It was part of the weight measured out of the tank- so suck as much of it in as you can...then release quick connect from high side- much easier (now with pressure in hose equal to suction pressure) and put cap on high side- then shut off low side on car and release and out cap on low side- ALWAYS put caps on- they are your primary seal to hold refrigerant in your system- as well as used to keep dirt out...

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Notsobright on Sat September 05, 2015 7:11 AM User is offline

Appreciate latest post. However my master cool gauge set does not have shut off valves at a/c ports.

GM Tech on Sat September 05, 2015 8:18 AM User is offline

So your hoses "vent" all the refrigerant in them when you release them from the car? Whoa- I thought that was an 80's thing that was taken care of with check valves on all hoses......perhaps they have check valves in them that you don't realize you have-- even the old R-12 hose sets came with check valves in the mid 90's.....

Check valves will do the same as what I described above, just remove the hose from the high side first.....

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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