R134 VA system charging,

[badazz81z28]

So I’m curious. You see so many off the shelf charging systems that come with gauges to charge “until your in the green” and others like VA give you the weight. I’m looking at R134 cans and some are 20oz but the back of the bottle says 18oz R134 and 2oz of additives. Do I just go off the R134 # or total of oz? Also why can’t i use the home systems and charge until the gauge shows green? Seems a lot easier than trying to measure by weight which I think would be less accurate. I have my system sealed and Evac all ready to go. Just needs Freon.

[dhutton]

Vintage Air operates at different pressures than an OEM system so the gauge does not apply. The margin for error is also smaller as I understand it.

You can buy R134A without additives. If you don’t have a VA supplied compressor you will need to add the correct amount of oil when you charge it.

Don

[ULTM8Z]

just get two 12oz cans of pure R134 and empty them in.

VA and CAA operate on the same basic type of system IIRC, and use 24 oz of refrigerant.

my guess is VA pre charged the compressor with oil, in which case dont add any more oil as you'll decrease the efficiency.

[badazz81z28]

Is it what VA does or Sanden? When I got my supplies compressor from VA it was sealed in a box, same as my Sanden...VA opens them up and pre-oils them?


Vintage Air operates at different pressures than an OEM system so the gauge does not apply. The margin for error is also smaller as I understand it.

You can buy R134A without additives. If you don’t have a VA supplied compressor you will need to add the correct amount of oil when you charge it.

Don

[ULTM8Z]

well, I guess what I meant was that the compressor they sell are probably pre charged. it should say in the instructions.

otherwise give VA a call and ask.

[badazz81z28]

Gotcha, sold my original compressor. I have a new Sanden. The instructions on their site do show their compressors come with oil.

[ULTM8Z]

yeah the OEM sanden I bought was also pre charged as well.

[dhutton]

just get two 12oz cans of pure R134 and empty them in.

VA and CAA operate on the same basic type of system IIRC, and use 24 oz of refrigerant.

my guess is VA pre charged the compressor with oil, in which case dont add any more oil as you'll decrease the efficiency.

Vintage Air states 1.8 pounds, 28 ounces and they are pretty clear on the need for it to use that exact amount....

Maybe the OP should ask VA....

Don

[sccacuda]

Most compressors come pre charged with oil, but how much? Use a paint mixing cup or measuring cup and drain the compressor. It helps to turn the compressor. Measure what comes out. If it's a new system, then you need to add the required system charge of oil. If it's a unit that has been in service, measure and replace just that amount of oil in the old compressor and put that amount in the new compressor.
I have to do this on every system I work on. If you replace a component of the a/c system, drain it and replace that amount of oil in the new part as well.
VA systems are "big" by todays standards, but still small as compared to R12 systems. Charge is pretty critical. 3-4 ounces one way or another can either slug the compressor or cooling will be poor.
Evacuation is the most critical. Despite what some people think that you are sucking out stuff, what your really doing is lowering the vapor pressure in the system. This allows water to boil at temperatures under ambient, turning to steam, and easily removed from the system through the pump.
Your ahead to just pay someone with a charging station that can evacuate and charge the system by weight. Just my $0.02.

[badazz81z28]

So, if that’s true why would VA assume the liability to tell you not to add oil? If the servicing is so critical, why is the DIY market so big? Everyone sells R-134 cans and servicing ports. You even see this stuff in grocery stores.

[sccacuda]

So, if that’s true why would VA assume the liability to tell you not to add oil?

Because they have there systems setup to use the oil amount precharged in the new compressors. Still should verify the oil amount in the compressor vs. what the system calls for.



If the servicing is so critical, why is the DIY market so big? Everyone sells R-134 cans and servicing ports. You even see this stuff in grocery stores.

I guess you could say no more critical than building an engine. Why buy or use precision measurement tools when you can just buy Plast-Gauge?
The people buying the freon charge kits are the same that buy block and radiator sealant. They don't want to spend the money to fix their A/C systems, so they just throw in some freon. It works on the same principal too, you know your A/C system has an issue, so your not mad if it doesn't cool correctly, or at all. You already knew it had a problem. Same with block/radiator seal...

I'm just trying to help you and tell you the correct way, if you don't feel it's necessary, then don't do it.

I'm betting you'll be the guy posting in a few days, "Help, Charged my A/C and it doesn't cool very well".

[badazz81z28]

Because they have there systems setup to use the oil amount precharged in the new compressors. Still should verify the oil amount in the compressor vs. what the system calls for.




I guess you could say no more critical than building an engine. Why buy or use precision measurement tools when you can just buy Plast-Gauge?
The people buying the freon charge kits are the same that buy block and radiator sealant. They don't want to spend the money to fix their A/C systems, so they just throw in some freon. It works on the same principal too, you know your A/C system has an issue, so your not mad if it doesn't cool correctly, or at all. You already knew it had a problem. Same with block/radiator seal...

I'm just trying to help you and tell you the correct way, if you don't feel it's necessary, then don't do it.

I'm betting you'll be the guy posting in a few days, "Help, Charged my A/C and it doesn't cool very well".


FWIW, I charged my first VA set-up. I’m looking for an easier way because trying to measure 12z cans was a PIA

[dhutton]

I use a little ebay drug dealer digital weigh scale. I know the weight of the empty can and compensate for it.

I also have a set of gauges and a vacuum pump.

Don

[dhutton]

Autozone will lend you gauges and a vacuum pump no charge.

Don

[AU Doc]

I'm going to be charging a CAA system pretty soon. My plan was to just take it to a shop and have them do it, but after reading this thread I'm not so sure that will work out as well as I would hope.

[ULTM8Z]

Vintage Air states 1.8 pounds, 28 ounces and they are pretty clear on the need for it to use that exact amount....

Maybe the OP should ask VA....

Don

hmmm ok... so I guess they take a little more than CAA.

- - - Updated - - -


I'm going to be charging a CAA system pretty soon. My plan was to just take it to a shop and have them do it, but after reading this thread I'm not so sure that will work out as well as I would hope.

itll evacuate just like any other system. for charging, simply show them CAAs instructions on how much to put in. they should know what to do. its not that complex...

[badazz81z28]

I would be worried a shop would mess it up if VA pressures don’t align with norms

[ULTM8Z]

I guess it depends on what they're instructions say. CAA seems to be more focused on the amount of refrigerant. they do give pressures, but it seems like more of a back check to see if there's anything wrong with the system.

basically put in 24 oz and you should get these pressures. as opposed to saying put in refrigerant until you get these pressures.

[Vintage Air tech.]

When topping off a system most often the LS/HS pressure will be monitored to dial in the capacity or witness performance issues, But when charging a dry system the only way to know that you have the correct capacity is by the weight. Once the recommended refrigerant (by weight) has been added the pressures will tell you how the system is performing. When the Vintage air system has the correct charge and the components are working as they should you should see 6-20 psi for the low side and double the ambient temp. + 15-20 % for the high side. The Sanden Compressors will come from the Sanden factory with the proper amount of oil (7.2 oz. PAG 100) If you have lost any oil or are concerned with the oil charge you could always remove the drain plug from the body of the compressor and drain out all of the oil and add 7.1 oz. back (minus .1 oz. for oil film remaining)

[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?

[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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