R134 VA system charging,

[badazz81z28]

So I charged the AC system, of course like last time, blew an O-ring with only 6oz added to the system. I did my best to get the recommended 28oz in, the system blows cold and the pressure readings are about right. The only thing is at 1500rpms, the low pressure is about 23-25psi compared to the recommended 6-18. Could be my Harbor Freight Gauges accuracy. Any who is this PSI something to be concerned about?

Also....why is VA different than the standard. According to all the research, the low pressure also varies by ambient temp. Why would R134 operating temps be different on VA systems? Also if R134A needs to be so precise, how do you compensate for different length hoses, compressor size etc.

also some videos tell you to validate proper servicing by system pressures, yet not for VA. AC pro says it’s common to over fill the system because people try to add specific amounts and state you need to use pressures.

Im trying to learn and understand, it just is confusing.

[GoodysGotaCuda]

Also....why is VA different than the standard. According to all the research, the low pressure also varies by ambient temp. Why would R134 operating temps be different on VA systems? Also if R134A needs to be so precise, how do you compensate for different length hoses, compressor size etc.

also some videos tell you to validate proper servicing by system pressures, yet not for VA. AC pro says it’s common to over fill the system because people try to add specific amounts and state you need to use pressures.

Im trying to learn and understand, it just is confusing.

I would say that the pressures depend quite a bit on the expansion valve orifice, efficiency/size of the evaporator as well as the condenser. I've found mine to be best by just trial and error with a digital thermometer in the vent and adjusting pressures to see which way it's trending.

I'd struggle with recommending a one-size-fits-all charge weight for these setups, they all will vary slightly with custom tweaks.

[dhutton]

VA runs different pressures to compensate for the smaller evaporator as far as I know. The lower pressures have less margin for error as far as I know and that is the reason for precise charging by weight.

When you measured your pressures did you have the windows rolled up and the fan on max? A large fan blowing into the front of the car will help a little too.

That being said I’ve installed quite a few VA systems and I don’t think I have ever seen 6 psi on the low side. Curious if anyone has...

I charge by weight per the VA instructions.

Don

[badazz81z28]

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