Quick A/C filling question
 

I'm using a manifold gauge set. I have pulled a vacuum for about 1/2hr, closed the manifold valves and it has held for about an hour now. My question is: Do I start filling with freon while there is still a vacuum in there, or open the valve and release the vacuum first?

Keep the vacuum--it will "pull" the first can of freon.

Hook up the freon/pierce can and crack open the hose for an instant by the guages to remove hose air before you fill with freon.

GL
John

Great, thanks!!

(I was thinking it might through off the PSI reading when filling)

As you charge the first can you will see the low side jump to about 70-80 with the high side slowly rising, then the low will fall off. The can is near empty, move onto can #2 and let it go, when no more will release, close the low side valve, fire up the compressor, open the low valve, and let it suck the remaining 15-16 ounces in.

Edit: I forgot to mention that it is a good idea to crack the charge line (or depress the schrader valve on the gauges, if equipped) after you puncture the first and remaining cans.

Wish Idda seen your post before I started filling it.

I turned on the a/c before filling, then I saw the quick rise on the low side. I was a little worried because the instruction card on the manifold said not to exceed 40psi.
I got about one can and a half in there and it's already reading 275 high and 40 low. It's 90deg and about 80-90% humidity. I'm reading it at idle. Clarks chart shows it should be 35-40psi and 190-225 psi.
I saw a post by John that says you should read the gauges at 1500rpm, not idle. I went back out and reved it up some, the low went down to about 20-25 and the high didn't change. I shut it off and stopped there.
I guess my next step tomorrow would be to add more freon while watching the gauge at 1500rpm? Might the high side drop some?

If you are using your gauge set correctly, and the high side gauge is not faulty, your high side pressure is too high and I would not suggest adding any more refrigerant. If the system does not have any air or moisture still in it (simply pulling a vacuum to 30 inches of mercury for 1/2 hour does not guarantee complete evacuation of non compressible 'gases') verify that your condenser fan motor is operating.

Remember when you charge a system with refrigerant:
Liquid through high side only with engine off.
Gas through either low or high side with engine off.
Gas through low side only engine running.
"Liquid" means can upside down.
"Gas" means can right side up.

How much refrigerant will you need, excluding that which you need to purge your service hoses? Look at the refrigerant sticker on the car, for example, if it says R12 '36' ounces, and you are converting to R134a, multiply the 36 x .85 = 30 ounces. This will be the 'general' starting point of the amount of refrigerant the system will use ... plus or minus an adjustment based upon a P&T or pressures and temperatures chart.

PM if you need help.

From what you just said about the can being upside down and right side up, I'm sure I did not fill it correctly. I'm going to do it over again this weekend, and pull a longer vacuum also.

If you attempt to push liquid refrigerant into the 'low' side of the compressor you can damage a reed valve and wash the oil coating out of the compressor.

If you attempt to charge into the 'high' side when the compressor is operating the higher operating pressures of the compressor could expand your little refrigerant can quite easily.

Wear a pair of safety glasses to protect you eyes and a pair of gloves for good measure.

Remember, if the system was low on charge the charge went somewhere along with the refrigerant oil, you need to add oil as well.


Suggested Reading:
Snap On Technical Training Systems - Air Conditioning , PN ACT279B
Published by Mitchell International

That brings up another question I had. How do you tell if you have enough oil in the system?

Actually that is a very good question. Time to think about this 'ey'!

Now what type of oil to use?: for R12 you can use either mineral oil or ester oil because the two types can live happily with each other. If the car has been converted to R134a and someone wisely put the blue sticker in the engine compartment documenting what kind of oil they put in and how much or you have repair record and they recorded it wisely on it, then you just have to use that type of oil. And, in this case I would play it safe by adding 4 ounces of oil and ignore how much may been injected with previous trials you have been doing.


Here is the clincher, some TS Bulletins state to use 'x' or PAG, however most PAG oils and R12 mineral oil don't live happily together (like a bad divorce... LOL).

Some little refrigerant cans can have either ester or PAG type oil.

Maybe you know whats in there or maybe you are guessing. I'd rather not guess and end up with the Gulf in my ac system.

So, if this is a 'real' first time conversion from R12 to R134a and you are using little cans of R134a and the can tells you what type of oil is in it, then I'd say
I want 4 more ounces to play it safe rather than be sorry with a toasted compressor.

On the other hand, if you don't know what you got and you want to save your compressor and lots of time down the road... then its time to liquid flush and for that I suggest you PM me with an email and note copy of this dialog attached.

OMG, I broke 700 ! Send me a Becks will you

I had the system converted to R134 a few years ago by a shop, but they didn't put any stickers anywhere. (they also put the wrong adapter on the high side fitting, it's a quick connect adapter, but the smaller low side size.)

I had to take the compressor off to drill out a broken bolt in the front mounting ear. It was also not cooling well, so I didn't mind doing this job.
When I had the compressor out, I dumped the oil in a cup and replaced it with the same amount of new oil plus a little extra. It's around 5 ounces of new oil. I used PAG 100.
The R134a cans I'm using are DuPont Suva from Auto Zone. I read the can, (with a magnifying glass) and couldn't find anything that says it has oil in it.

Should the 5oz I put in be enough? If I need to, is there an easy way to add oil?

Short answer: you should be fine to go with your 5 ounces.

Long answer below:


From our experience on a conversion or retrofit from R12 to R134a in 924s, 944 and 951 (all share the same ac system components), adding 6 ounces nominal of 'polyol ester' or Ester oil seems to provide enough lubricant to the system; this assumes you disposed of what ever residual oil that was in the compressor (by inverting the ports over a collection can, turning the outer hub several times and changing the position or angle of the compressor to assist in draining; typically you don't extract much oil from a compressor, an ounce or two would normal if any) and you have replaced the receiver drier.

The issue with small cans of R134a (vs. a 30 lb container) is that some retail brands have optional additives such as refrigerant oil, sealants or 'enhancers'. Frankly sealants should be avoided as studies have shown they can clog up other things besides leaks in a system, such as your expansion valve and compressor. I have yet to observe any performance gains from 'enhancers' (I guess we have to set up a lab for that one... LOL). But back on the subject of oil additives the question is what kind of oil? Is it PAG or Ester. If contained in the small retail can the additive should be noted on the can; you could search the MSDS (Material Safety Data Sheet) on the product however MSDS on retail packaging sometimes can be a headache to locate; you may find the chief component but not the additive noted on data sheet).

The issue with systems having R12 'mineral' oil (naphthenic, paraffinic, and alkylbenzene) is that it has a very poor solubility with R134a. Since the compressor does not have a sump to hold oil the system relies on the refrigerant flow from and back to the compressor to carry oil through the compressor to lubricate it, hence the oil must be soluble or blend in with the refrigerant.

The first conversions from R12 to R134a used PAG. PAG lubricants can come under attack from chloride residue trapped in residual mineral oil (such as in the drier, hose lines, compressor and evaporator) in systems that previously used R12. The PAG or its moisture content may also affect compressor materials. So an extensive cleaning or flushing of the system was required. With the introduction of Ester oils it was found that esters are not as sensitive to low or residual mineral oil concentrations; esters get along better with mineral oil.

Some compressor manufacturers specify PAG and some Ester, it all depends upon when they did their studies. However we have been using Ester for retrofits for the past 15 years with little if any problems. Problems encountered with converting from R12 to R134a fall into two categories:
The first is performance. On front condenser cars such as early water cooled Porsche's (924s, 994 family and 928) we have experienced little if any performance loss. On air cooled Porsche's (911,930) the performance problems are from the inadequate existing design (insufficient condenser and evaporator)
On the water cooled cars a drop in observed performance is usually caused by not following procedure, such as adding too much oil which insulates the heat transfer in the exchangers (condenser or evaporator), inadequate evacuation (leaving residual R12 trapped in the residual oil, moisture or air), under or over charging.
The second problem is component failure, typically a crashed compressor. In most cases the compressor was old and worn to start with, or there was metal particle contamination in the system, residual 'funk' (bad oil junk) or poor oil flow.

Follow the right procedures and you should be successful.

kuehl,

Please correct me if I am wrong.
The correct PAG oil used for our conversions should be PAG 46 which is the interchange for the oil Porsche uses--ND-oil 8.

The PAG oil used by marco was PAG 100 and this may be too thick for our compressors.

Also, the oil should be put in different components. 2 or 3 ounces in the compressor, an oz in the dryer, and ounce in the condensor and if possible an ounce before the evaporator/expansion valve (or it may never get there)

If marco put 5 ounces in the compressor, he has to spin the compressor free hand a many, many, many times before starting to avoid damage to the compressor.

Even still, there may be damage to the compressor with use of the wrong weight of PAG oil.

John

Please correct me if I am wrong.
ND8 vs. PAG46
I am not a favor of PAG because of the issues noted.
"ND 8" has been quoted from various sources to be same viscosity as PAG46 however I have not compared the two data sheets from various manufacturers or private brand suppliers to verify it. But, we'll assume it is for sake of bandwidth.

The PAG oil used by marco was PAG 100 and this may be too thick for our compressors. Maybe. You could run a side by side study on 'new' identical compressors under identical conditions and compare the outcomes.
I would be concerned if the evaporator core temperature was low.

Also, the oil should be put in different components. 2 or 3 ounces in the compressor, an oz in the dryer, and ounce in the condensor and if possible an ounce before the evaporator/expansion valve (or it may never get there)
I would never waste my time with such a strange procedure since the oil and refrigerant with become homogenized throughout the system shortly after running it. Oil is usually introduced, or simply introduced, into the system by simply putting the required amount into the compressor (DIY), or having your ac tech inject the oil after evacuation.


If marco put 5 ounces in the compressor, he has to spin the compressor free hand a many, many, many times before starting to avoid damage to the compressor.
Your probably referring to possibility of 'slugging' compressor's reed valves, which can occur with a heavy oil load or when you mistakenly put liquid refrigerant through the low side. Usually a few hand turns is enough move excessive oil past the reeds but many have not and have not damaged the reeds, but a good concept to follow in practice.


Even still, there may be damage to the compressor with use of the wrong weight of PAG oil. The condition of the compressor prior to doing any procedure is normally considered by those who have 'been there and done that'.
A savvy DIY would consider the mileage of the compressor and inspect the compressor ports and residual oil for signs of contamination.

Where is my Becks?

704 posts and you expect a Becks-----maybe a wine cooler. You are from the class of '04, not officially an 'ol timer ;)

I understand your use of esther oil. It mixes better with R12. If the system is not flushed correctly esther oil should be used.

marko used PAG 100, this is why I wanted your opinion on the weight of the oil.

AutoZone sells PAG in 3 weights (46-100-150) ---on the same shelf----you could accidentally grab a can of PAG 150 without looking and use it-------------BTDT. The compressor will overheat or the oil will clog the system.

Filling oil.
If the compressor is off, and PAG 46 is chosen, the compressor should be rinsed with new PAG 46----not AC flush and refilled with 2-3 oz of PAG 46

A new dryer should get 1 OZ

The condenser should be properly flushed with a cheap can of AC pressure flush (~$20) from AutoZone to get the residual R12 mineral oil out of the bottom line.
Pros-kuehl, have a solution in bulk--maybe some denatured alcohol.

After the condenser is flushed new "O" rings used (AutoZone small pack $6) and insert an ounce or so in the condenser. You should replace the 4 "O" rings on the compressor manifold--get 2 small packs of "O" rings.

Stick another ounce in the condenser discharge line to the evaporator.

This is my procedure. It may be a waste of time. I do understand the Professional AC technician with the quality of tools and unknown voodoo machines used will consider this overkill. On the forum, I revert to a basic technique that a garage, novice experienced, member can understand.

Thanks kuehl, cheers!

John

704 posts and you expect a Becks-----maybe a wine cooler. You are from the class of '04, not officially an 'ol timer maybe on this forum 04... , I guess
I'm not qualified to answer ...LOL , Sorry, no wine coolers are allowed in our facility.

I understand your use of esther oil. It mixes better with R12. If the system is not flushed correctly esther oil should be used.
Most DIY questions that you will read on forums never address 'flush' and I doubt you will find any majority doing it, hence ester.


marko used PAG 100, this is why I wanted your opinion on the weight of the oil.
and?


AutoZone sells PAG in 3 weights (46-100-150) ---on the same shelf----you could accidentally grab a can of PAG 150 without looking and use it-------------BTDT. The compressor will overheat or the oil will clog the system.
maybe! but doubtful, most DIY will hit a big-box store and big-box stores normally limit inventory to 46 or 100


Filling oil.
If the compressor is off, and PAG 46 is chosen, the compressor should be rinsed with new PAG 46----not AC flush and refilled with 2-3 oz of PAG 46
I would be interested in hearing on how you are going to successfully "rinse" a compressor.

A new dryer should get 1 OZ
Your reflecting upon the estimated ratio of oil required for each component.
How would you handle an unknown system, one that has no documented history?
So far with the compressor and drier you are only up to 3 to 4 ounces total system based on your procedure. If the system has had a terrible history, which is common on 944's based on the ownership turnover you are going to have a problem with only 3-4 ounces way down the road.


The condenser should be properly flushed with a cheap can of AC pressure flush (~$20) from AutoZone to get the residual R12 mineral oil out of the bottom line.
Pros-kuehl, have a solution in bulk--maybe some denatured alcohol. The issue that arises when using flush agents that are not compatible with the refrigerant and its oil, problem is residual flush agent. For instance, I recall a chap who liked Tri-hlor 111, the problem is it permeates into the rubber hose and then mixes with the refrigerant to form a funky gas that does not have the same characteristics as the single component refrigerant.

After the condenser is flushed new "O" rings used (AutoZone small pack $6) and insert an ounce or so in the condenser. You should replace the 4 "O" rings on the compressor manifold--get 2 small packs of "O" rings. Well we are up 4-5 ounces of oil. Looking better for sure. Although it is better to replace the stock o-rings with a HNBR (hydrogenated nitrile rubber) when converting to R134a, the rule is "if it has not been opened you typically don't have to replace it" because it is a static seal and the surface that is exposed to refrigerant is limited. But if you have the time 'go for it'. Might as well note the sizes why we are here:
Compressor hose connections: (1) #8, (1) #10
Drier: (2) #6
Condenser: (1) #8, (1) #6
Expansion valve inlet: (1) #6
Expansion valve outlet: (1) probably #8 (have fun changing this one based upon the model year)
Evaporator outlet: (1) #10
Compressor manifolds: on a 10P15E or 6E171 (4), WA when I get my beers.

Stick another ounce in the condenser discharge line to the evaporator.
Get out the syringe boys!


This is my procedure. It may be a waste of time. I do understand the Professional AC technician with the quality of tools and unknown voodoo machines used will consider this overkill. On the forum, I revert to a basic technique that a garage, novice experienced, member can understand.
Voodoo machines? Is that what we call those little rice rockets that pull up next to us at the light?


Thanks kuehl, cheers! I can't toast cause you ran up a tab here.

John

Thanks again kuehl,

We have raised some additional questions that certainly has marko scratching his head. I will now go in a corner and welcome your advice.

John

I was driving down a country road once and past a sign in front of church.
The background they had painted in had a shadow of book and the foreground
big bold letters. As I drove away all I could say was 'friggin fantastic advertisement!'

What it said kinda applies to everything we 'should' do.
It said simply..... Read the Instructions

Suggested Reading:
Snap On Technical Training Systems - Air Conditioning , PN ACT279B
Published by Mitchell International

Interesting, although I take the necessary steps with other's vehicles, I can accept compressor failure when I do things my way, on my own cars. My attitude towards the whole ordeal mirrors how I feel about timing belts, why make things complicated, it's a rubber belt.

Through my own testing, mixing oils makes not one bit of a difference. We have an a/c tech within our corporation that helped design a/c systems for several manufacturers, he'd probably say I'm wrong and catastrophic failure is inevitable. I'd tell him the background on my system and offer a ride.

I remain on the side proclaiming that it's a bunch of bs, and that will most likely be where I stay until we see shade tree results with the incoming hfo1234yf refrigerant.

Do what you want.