Automotive Air Conditioning Information Forum (Archives)

LoJo on Wed August 25, 2010 7:26 AM

Year: 1993
Make: Corvette
Model: LT1

Could anyone tell me what the procedure is for re-gassing a system that has been stripped?

I have totally rebuilt my compressor after a front seal leak (no breakdown debris in system), blown through (compressed air) the condenser and evaporator (no oil or water seen coming out), fitted a new acc/drier and orifice tube plus all new seals.

The system was R12 which is no longer available where I live, so the system will be refilled with R134a, new seals are compatible and adaptors have been changed.

I’d like to go to the garage with some idea of what they should do and in what order. Could anyone tell me:-

Should I put the correct quantities of oil (DEC-PAG) in the compressor, drier, evaporator and close the system prior to going for the re-gas?. Should the garage purge the system with OFN to remove any moisture or will a vacuum do this (if so how long should it be applied). Would OFN and/or a vacuum remove the new oil if I pre fill the system?

I intend to ask the garage to initially charge with R134a at 65% of the R12 spec., and test from there, does this sound about right?

Any info, or anything I’ve missed… appreciated.

Thanks.

emsvitil on Wed August 25, 2010 8:13 AM

Get your EPA 609 certification and you can get R12 off of Ebay.

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Ed
SoCal

iceman2555 on Wed August 25, 2010 9:25 AM

Blowing compressed air thru a system accomplishes little if nothing to remove debris or residual lubricant. The system should be completely flushed with a suitable flush chemical. Then air purged to remove all residual flush chemicals.
The system will perform better with 12. However, since it may not be legally available in your country (unknown) then the recourse is to use 134a or some other refrigerant. Suggest to stay with 134a...not all SNAP approved chem's are good the system. Keep in mind that a SNAP approved chem is approved for EPA regs...not system performance.
A charge rate of app 90% should be used. 65% is too lite and will result in compressor failure due to lack of lubricant migration.
There a several post on this site concerning 'retro-fitting'....complete a search and study them.
Lubricant added to the system needs to be in two locations only...the compressor (2-3 oz) the remainder can be added to the inlet side of the new accumulator. The system will balance itself. This is of course, after the system has been cleaned to totally remove all traces of mineral lube.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Wed August 25, 2010 12:03 PM

Thanks iceman & emsvitil,

No R12 in Spain and no certification to obtain it.

Iceman, this is where I really get confused: The official GM service manual say’s “Important – Oil Distribution” and then say’s add oil… Comp: as removed + 1oz, Evap: 3oz, Cond: 1oz, Accum: 3.5oz, is it safe to ignore that and add just to the comp & accum as you suggest?

Another thing about the manual… it specs quantities at 8oz oil, 2 1/4lbs refrigerant, however adding the top list of quantities together gives a total of 8.5oz plus whatever was in the comp., which is .5oz over the specs., without what was in the comp!. I really confused as to how much oil and where now, especially as I couldn’t accurately measure the drained oil from the comp… any suggestions please? (Denso 10PA20C comp., totally drained and dry).

Sorry to go on about GM specs, but I’m told they issued a bulletin saying not to flush the vette systems on a retrofit, but to use compatible Ester oil. I thought Double End Capped PAG-46 would be better and still not need a chemical flush… am I wishful thinking?. There was no compressor breakdown, no debris, particals, crud or even any signs of dirt in the system (comp, orifice filter… nada) when I stripped it down.

I have all the components stripped out at the moment, evap, condenser, lines, so I could easily flush a degreaser -> water -> air through the parts… good/bad idea, or should I stay with GM’s no-flush routine?

Problem always in Spain, is no garage (local anyway) wants to work on a vette or do it properly!

Thanks for any suggestions.

iceman2555 on Thu August 26, 2010 8:00 AM

The issue with 12 in foreign companies can be serious problem for older vehicles.
If money is not a serious issue, and yes, I know that sounds completely insane. Research the possibilty of changing your condenser to a more moder design. I am not sure what condenser was used in the 93's. Some of these late model 12 cars were actually spec'd for 134a. If possible post a photo of your condenser...we should be able to ascertain the design. If the condenser is, indeed, the standard tube and fin GM 12 type condenser, then the change of this one item to a more efficient condenser can make a significant difference in your system performance. Another issue to consider is your seasonal temps/humidity factors.
When the 'retro fit' craze hit the market in the 90's, most OE's did not have an 'official' retro fit procedure. There contention was that as long as r12 was available, the dealers should service the system with 12....did they know something we did not??? Yes, what the OE engineers knew was that to properly retro a vehicle....basically the entire system needed to be upgraded. If this was not true then why did the OE's then and still today, constantly refine the AC system. The major problem with the use of 134a in the 12 system is the ability of the condenser to accomodate the excessive high side pressures of the new refrigerant. These units simply lack the ability to properly condense 134a. Recharging to a lesser amount of refrigerant was an 'attempt' of the aftermarket to 'force' the system to function with this new refrigerant. The balance act of adjusting charge rate to pressure/temps and still maintain total system operational parameters was extremely critical. Everyone (OE's, parts mfg'er's etc) had a different approach to the correct procedure.
At first, when it became evident that vehicles were to be reto fitted...the inital procedure was to replace the condenser, hose assemblies, ADRD's, the evap and serice. The estimated cost of this procedure was quite expensive....estimates were in the low $1000.00's and higher. The outcry was trememdous....everyone began to 'search' for a 'workable' procedure. It seems each mfg'er had a different procedure....but also keep in mind that the OE's still recommended to maintain 12...however, if the customer desired...the procedure was if the vehicle had less than 40K miles, the system was not even opened up...the refirgerant was recovered, system evacuation, add 8 oz of PAG (SEC in that period of time), and recharge with app 75% 134a to 12 specs. The serious undercharge was to accomodate the additional 8 oz of lube. Remember they did not flush the system...so all the remainding mineral lube stayed within the system. Basically the system was overcharged with lubricant and undercharged with refrigerant ....it was believed that this condition would result in an acceptable cabin temperature and still maintain operational pressures/temps and most important.....compressor longevity. Chrysler basically stated....DO NOT RETRO FIT OUR VEHICLES. Ford...similar to GM. But ALL wanted to use 12 as long as possible.


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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Thu August 26, 2010 10:12 AM

Iceman, thanks for the detailed info… appreciated.

I’ve actually already battled with many of these problems during this ‘exercise’. I would prefer to stay with 12, but not an option, I do have a T&F condenser, but as far as I can find out (extensive searching) there isn’t a replacement. It was suggested to fit a 94 or later condenser, I investigated that option and found out (stripping the lot to bits) that the vette condensers (and cooling rads) are not bolted to anything, they sit in a molded fiber-glass surround supported only by rubber… the later ones are different and it would be one hell of a job to fabricate a new support system!. So I’ve gotta try and make the best of what I have.

That leaves me with the confusion of how much oil and where to put back in the system, whether to flush or not (both given the GM specs/recommendations above and your advice) and what I should be watching the garage do by way of re-charge procedure…

Should I ignore the GM manual and just put the oil where you suggest and is it best to also ignore GM and go ahead and flush (even with DEC as the new oil)?

Any thoughts please.

iceman2555 on Thu August 26, 2010 11:13 AM

Part II
The key to a successful retro is to maintain proper lube flow....governed by the correct amount of refrigerant.....and of course....cool the darn vehicle. Requires quite a balancing act.
Changing the condenser to a more efficient heat exchanger is one of the best methods to insure a good operational long lasting system. In many cases, when the condenser is replaced, the conception of 'undercharging' is gone....the system will normally function with a full 134a to 12 recharge ratio. The key is sufficient refrigerant to maintain lube flow.
Lube for this vehicle is 8 oz. 3-4 in compressor suction side....the remainder into the inlet of the accumulator. No need to put some here...put some there. The spec's indicated are normally the amount that should be added if that component alone is changed. The key locations for lube are the AD and compressor. The AD acts as a reservoir for the compressor lube.
If the condenser is not be changed....start with a recharge of app 90%.....remember to add for the refrigerant necessary to pre charge your hose/manifold assembly. Once this is completed..operate the vehicle for app 5 minutes...MAX AIR, HIGH BLOWER,DOORS OPEN, ENGINE @ IDLE.
Obtain a method to determine surface metal temperature. Determine the inlet and outlet temps of the evaporator. These temps should be the same...or within 3-5 degrees of each other.
When this condition is met, the system is fully charged. If pressures are excessive...do not remove refrigerant....increase condenser cooling....not sure how to accomplish this on a Vette...already has a good electrical cooling fan.....hopefully this will not be an issue.
Denso compressors normally require PAG46, however, I shall check with our engineers to determine if this is also a requirement for the older units.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

iceman2555 on Thu August 26, 2010 11:20 AM

A good flush is essential. Keep in mind that most OE do not recommend flush procedures after a severe compressor failure...the suggestion is to replace parts that maybe contaminated.
Let us know what flush chemicals maybe available in your market....perhaps we can offer some suggestion.
The issue with the condenser is totally understandable...GM does seem to 'experiment' with the Vette. It appears that the tube and fin will be the only recourse. I shall check with some condenser people to see if anyone makes a replacement.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Fri August 27, 2010 4:37 AM

Iceman, thanks again, great explanations and advice.

What I’m facing is a collection of strikes against me!... I have a make of car that no garage (locally) wants to touch, basically because they know nothing about vettes. What AC garages there are (again locally to me) in Spain are not what you would call inspiring … that’s saying it mildly/politely. I try ordering parts from the US and AC companies that I find and think are knowledgeable won’t ship direct out of the US. A major European AC supplier (Sunair) in Holland, is extremely helpful, but even their nearest ‘recommended’ specialist is 350miles away. Of course, add too that although I’m a reasonable mechanic, I’ve never touched an AC before… I believe in take it to the pro’s… when possible.

Anyway, I took your advice (best I could) and called a mobile AC company, their tech came and said he didn’t have the equipment to flush on site, so he has taken the condenser and evap away for flushing… I really don’t know if I can rely on him or know how it’s going to be flushed, but once again it’s the only option I can find and in all honesty it scares me a bit. Hopefully parts will be back later today or tomorrow.

Can I ask… when the parts come back, should I add oil (will add where you suggested) and seal the system, or do I need to get nitrogen into it or a vacuum before adding oil, so as to remove any moisture?

As a side note, I’m told that R134a is to be banned on all new production cars in Europe from January next year, is this the same in the US?. Boy are you right about this being a complex business for manufacturers and AC techs.

iceman2555 on Fri August 27, 2010 10:35 PM

If there is a local supplier for AC parts...I found two sources that indicate a high efficiency condenser for this vehicle. Most of the condenser (aftermarket) mfg'er have switched to making a more efficient condenser for earlier model vehicles. This part alone can make a vast difference in the performance of our AC system. It is a known fact that no one here likes 4Seasons, however, they may be a source for you. Check for their European division. They manufacture heat exchanges here in the US and should be available in Europe.
Sorry, TRB, simply trying to assist the man!!!!
Actually the method of installation of the condenser, the rubber mounts, makes it easier than one things to 'retro' fit a more efficient condenser. This has been a standard GM method of radiator/condenser installation for many years. It is quite easy to adjust these mounts to mount a slightly different cooling unit. Look it over very carefully.
The issue with the new refrigerant, HFO1234yf, damn..why can they not leave well enough alone. The Europeans decided that 134a was harmful for the environment...so they decided to change....and....thusly....seems as if we are also.....
Think 2012 is the cutoff for EU vehicles....and we should be in the new stuff about the same time.
The change over should be veryyyyyy interesting. The way it stands now....no retrofitting. Hope this stays in place.
Once your parts are returned....air drying with a constant supply of dry,filtered air is sufficient. Begin installation, add lube to the proper locations....complete installation, evac and recharge the system. Moisture only becomes a problem if the system is left 'open' for an extended period of time.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Sun August 29, 2010 7:37 AM

Iceman, have you ever had one of those situations where you don’t know whether to laugh, cry, or shoot yourself, I couldn’t help it and I don’t know if I took it out of context, but I fell about laughing… remember I said I had reservations about my local garages and taking that with your comment “Moisture only becomes a problem if the system is left 'open' for an extended period of time”… well I got the cond and evap back from being flushed and they’re both dripping out water (lots of it) .

I haven’t got a ‘decent’ filter on my home compressor, so I guess I now need to find a spray shop or somewhere to blow them thru… will this be ok?

They told me nothing (debris/dirt) came out of the cond or evap, is this possible?... I don’t know whether to trust their flushing or not!

Apart from the cond and evap moisture!, which I’ll get removed, the rest of the system has been ‘open’ for about a month, will normal vacuuming get rid of any other moisture in the system?... sorry I’m not clear on this because of read about nitrogen being used sometimes.


Thanks for the 4Seasons suggestion. I don’t know if I have the right company, I googled and the most likely candidates seemed Chicago and another in Florida. I also know of http://www.4s-europe.com/index.html... does this logo look like the company?
.
If so, I tried them a couple of weeks ago, not very helpful and when I asked if they did a parallel flow cond, they told me they only produce an OEM T&F and don’t have an alternative which seems to be confirmed by their catalog (http://www.4s-europe.com/media/pdf/GM.pdf ).

Perhaps your right about the R134a phase-out being 2012, but opinion here seems to be January next year. It’s bad enough for us guy’s not being able to maintain R12, but in some respects I don’t know if it’s a blessing!… on your side of the pond, you seem to have to deal with all sorts of refrigerants/systems and all the retrofits in between… sounds like a headache!

Sorry if I sound like I'm asking how to resolve problems relating to my location, this isn't the case, I'm just trying to learn how get right what I do have and what is available.

Edited: Sun August 29, 2010 at 7:42 AM by LoJo

iceman2555 on Sun August 29, 2010 4:49 PM

The issue with water in your system can be quite serious....but it seems that you have sufficient time to complete a drying process. Suggest to place the units in a high heat area...sunlight..not the oven....devise a method to air purge the components until no traces of water remain. As far fetched as this procedure sounds...have encountered it here in the good ole USA. However, the contaminant can be removed.
The issue with the condenser remains a point of interest. Is there a local supplier that offers OE parts? If so, why not check with them...determine if they may have the correct part number. If so, why not have the open the container for inspection and determine if it is possibly a more efficient unit. We recently purchased a GM unit for a earlier model vehicle...actually a 12 system on a GM Astro. When we opened the box....could not believe our fortune....inside was a true PFHE OE unit. Made the retro a breeze.
The phase out of 134a from the OE should not seriously effect the availability of 1234yf....from my understanding 134a will remain as the refrigerant to use with 134a vehicles...from cradle to grave.
One other concern with your vehicle..is this not an Automatic Temperature Control AC system?

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Mon August 30, 2010 5:39 AM

Oh no!... I was laughing at the water they left Iceman, now I’m not so happy if it can be a problem. I’ll do as you say… we have hot weather at the moment, so I’ll give the parts an initial blow thru and then put them in the sun, before getting them blown thru again with filter air.

I have absolutely no local vette suppliers (UK, Holland and perhaps France are nearest), so can’t get a crate opened? . I have spoken with the UK dealer (who is pretty good) and he say’s he doesn’t know of a drop-in or even a drop-in’ish alternative.

I have two options at the moment (neither ideal), 1. run it up with 134 on the original condenser and see what it performs like or if it don’t work 2. I’ll rip the entire system out and go without AC. Actually, there might be one other option… don’t know if its feasible or financially viable?, but to get a condenser custom made or one from another make of car altered!!??, but before I even think about that, I guess I should try option 1.

Sorry again to ask another question, but going back to the actual re-gas procedure… after getting the garage to follow your advice above, is there a test of some sort I should ask them to do?... I’m thinking about all these pressures and readings you guy’s quote. I understand what you have said about surface temps at the evap in/out, but should I also get the garage to note down pressures v temps and should they be able to adjust/balance these in any way during the re-gas. I feel better if I can knock on the garage door with a little knowledge.

I’m sure your right that topping-off with 134 will be good for a fair few years (until the powers-to-be wanna stuff us), but I suppose folks like me running an older car will always be running close to the wind… oh, perhaps a bit of wind might be a good thing if I’ve got no AC!

PS: sorry if I'm a bit slow in answering sometimes... time zone differences.

Edited: Mon August 30, 2010 at 5:39 AM by LoJo

iceman2555 on Tue August 31, 2010 10:15 PM

Check www.ecklers.com. This company in located in Florida and specializes in Corvette parts. They have an international sales division. The catalogue list a replacment condenser..check with them concerning the type. The photo is a PFHE unit.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

LoJo on Wed September 01, 2010 12:58 PM

Hi iceman,

I’ve tried Eckler’s (and Mid America Motorworks + Corvette Central + Jegs and a few others, all in the US and I’ve used these companies before), the general responses that I have received are… ‘we have no drop-in replacement and we can’t guarantee that a non specified year will fit’. Okay, I could try a later year, but all these companies insist on shipping UPS, which by the time taxes and import is added at my end means double the ticket price in the US, so we’re now talking about a $500+ condenser!. Okay, I ‘could’ go that route and expense, but if it arrives and can’t be made to fit, the US companies won’t (naturally) accept it as a warranty return, so I will have to forfeit the US -> Spain shipping and duties and also have to pay for shipping back to the US, or try to sell it in Spain, where vettes are rare!… don’t even know if there are re-stocking fees to take into account. It’d be easy (easier anyway) if I lived in the States. Its all darn, ‘locality problems’. Many thanks for thinking of it though.

I’m pretty much resigned to the fact that I’ve gonna have to try and see how the original condenser performs, I’m not too worried at a slight drop in performance. One thing the vette does have going for it is it’s a small cab to cool and in the pre strip-down state it was over cold.

I’ll report back on how it goes, but I wonder if you have any thoughts on the previous question about pressures/balancing etc and anything else to watch out for during re-gassing?.

Really do appreciate the interest and help you’ve shown iceman.

LoJo on Mon March 07, 2011 9:38 AM

Hi all,

Well, it's been a long time, but I promised to report back.

After rebuilding the compressor and fitting new hub/clutch, accumulator, orifice and all R134 seals, I left the A/C uncharged/untested whilst trying to source a parallel condenser... I had no luck, so this week I just took it to my local garage and had them vacuum and charge (R134) the system.

I don't know if I'm lucky, and accepted it's only in the low 20's C at the moment, but the system is blowing freezing cold even with the car stationary!

However...!!!, can I ask for some help/advice please:- I want to be sure that the garage has charged it correctly and the pressures etc are correct, but both the garage mechanic (Spanish) and me (English) are in debate about the GM service manual specs and converting them to metric (the garage gauges and recharge unit are all in 'bar's' and 'Kg')

I've attached a page from the manual and this refers to 'PSIG' (pound square inch gauge). Wiki says PSIG is NOT the same as PSI, but I see you guys usually refer to PSI when talking A/C. So questions are (please):-

1. Should I convert the PSIG readings from the manual to plain PSI and then to BAR or what???.

2. Do I need to convert the whole table or are there just a couple of readings I really need (eg parameters between high and low)?

Any advice much appreciated.



Edited: Mon March 07, 2011 at 9:45 AM by LoJo

HECAT on Mon March 07, 2011 10:45 AM

PSI = pressure/force in pounds per square inch
PSIG = Gauge - reads zero PSI at atmospheric pressure.
PSIA = Absolute - reads 14.7 PSI at atmospheric pressure.

I context of A/C work and advice given here; PSI and PSIG are the same.

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

LoJo on Mon March 07, 2011 1:31 PM

Quote
Originally posted by: HECAT
PSI = pressure/force in pounds per square inch

PSIG = Gauge - reads zero PSI at atmospheric pressure.

PSIA = Absolute - reads 14.7 PSI at atmospheric pressure.



I context of A/C work and advice given here; PSI and PSIG are the same.


Thank you very much HECAT. If anyone uses 'BAR's' does this table I've drawn up look correct then ?:-



Should I be asking the mechanic to aim for these figures now that it is R134 or do they need to be modified since they were for an R12 system?

Can I also ask another question:- should I adjust/replace the low pressure cycling switch for R134. I read somewhere that it can be adjusted to 21 psi.

Thanks again.

HECAT on Tue March 08, 2011 12:04 PM

Quote
Originally posted by: LoJo
Thank you very much HECAT. If anyone uses 'BAR's' does this table I've drawn up look correct then ?:-

Should I be asking the mechanic to aim for these figures now that it is R134 or do they need to be modified since they were for an R12 system?

Can I also ask another question:- should I adjust/replace the low pressure cycling switch for R134. I read somewhere that it can be adjusted to 21 psi.

Conversions to BAR seem correct. The R-12 chart is not relevant to R-134a and a R134a pressure switch is needed. Iceman posted the recharge procedure to follow in his third post to this chain.


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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

LoJo on Wed March 09, 2011 7:37 AM

Quote
Originally posted by: HECAT
Quote
Originally posted by: LoJo
Thank you very much HECAT. If anyone uses 'BAR's' does this table I've drawn up look correct then ?:-



Should I be asking the mechanic to aim for these figures now that it is R134 or do they need to be modified since they were for an R12 system?



Can I also ask another question:- should I adjust/replace the low pressure cycling switch for R134. I read somewhere that it can be adjusted to 21 psi.



Conversions to BAR seem correct. The R-12 chart is not relevant to R-134a and a R134a pressure switch is needed. Iceman posted the recharge procedure to follow in his third post to this chain.

Many thanks again HECAT,

Yes indeed, I have followed Iceman's instructions as best as possible (stumped with the condenser) and I am extremely gratefull for his, your and everyones advice... I wouldn't have been able to do any of it without the help so it really has been much appreciated.

I seem to always be battling with the way the local mechanics work on A/C. They don't seem to know anything about R12 to R134a retrofit (especially on a vette) and from Iceman's instructions I assume I need the A/C mechanic to experiment and balance the system to achieve optimal/safe performance... this the local guys don't seem to comprehend or want to be bothered with, so I am looking for some rough guidelines so that I can tell them what/how to get the best readings/performance:- ie: I don't know whether to tell them to aim for a certain (or max/min) pressure readings or best temps or a combo within a given range.

Are all R134a pressure switches the same PSI cut-off or do I need to find one of a certain PSI.

Sorry, they're probably basic questions for you guys and sound silly, but A/C is a black art to me and after getting this far I just want to get it set up right.

Thanks again