A/C - conversion to R134a

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A/C - conversion to R134a

Post by white exec »

About to get stuck into this, on the R12 factory system on the 19D Millesime.

Have read up on some of the past threads, including Dragon Man's 2016 one:
viewtopic.php?p=261690#p261690.

Can I just ask whether this is still the latest advice...
- renew the O-rings (compressor, dryer, bulkhead TXV) . . . fortunately, Citroen still list these all as available
- renew the dryer
- use PAO68 oil (I have the Behr-Hella document, which confirms)

QQ:
- Am I right in thinking there is only one evac/refill point on the BX system?
- Which of all the various adaptors is recommended for converting the connection point(s)?
- After DIY fitting of the new O-rings and dryer, and draining of the old oil, should I add the new PAO68 oil before or after getting the system vacuum tested for leaks?
- Whereabouts is the oil added?

Lastly, Citroen issued a Training document for the conversion of BX from R12 to R134a. Does anyone have a copy of the pdf?

Thanks :wink:
Chris

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Re: A/C - conversion to R134a

Post by Kitch »

Vanny and Mat F are the go-to guys on this, IIRC.
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Re: A/C - conversion to R134a

Post by Jaba »

I think it is more a recharge with a different gas than a conversion as all that needs to changed is the oil, dryer and charging port.

There are 14 o-rings to change. Any aircon supplier can fix you up. You will need several sizes 3 or maybe 4 I can't remember. They are coloured green for aircon.
R12 oil is mineral and PAG is not and they are not compatible so a good flush through is advisable or you can use Ester oil which is compatible with both. An aircon specialist or garage will only have PAG available - well around here in the Thames Valley anyway. Charging is only possible using the high side as there is no connector on the low side, it is possible to instal the extra one of course which will allow for vacuum readings and better fault diagnosis.

Yes a new drier is required. For charging the standard R134a screw on high pressure red coloured conversion connectors are all you can use on the basic schrader valve on the existing connection. They have been known to leak so buy a spare as well.

The oil goes in via the drain plug or during recharging but not with an empty compressor obviously. The quantity of gas to use varies with the type of condenser you have and who you speak to and varies between 550 and 800cc. It is not critical to get the correct amount though. The last time I had mine recharged the guy insisted that 550 was the correct amount and more would cause overheating even though I tried to insist on more than that. After a few weeks the system did not get cold enough as measured at the air vents. So I bought a recharge can from Halfords and pumped in over half of it to restore proper cooling with about 6deg at the vents.
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Re: A/C - conversion to R134a

Post by white exec »

Thanks, both, for the information.
The O-rings should be here tomorrow - Citroen have them all at a nearby branch.
Mister Auto have half-a-dozen listed dryers.
R12/R134a adaptors on Amazon.

I guessed there was only one port. Is that one used for both evacuation and filling?

"The oil goes in via the drain plug or during recharging but not with an empty compressor obviously."
Not sure I understand this...
- how would you fill via a drain plug?
- and, should the new oil go in before a vacuum leak test is done, or afterwards?
If oil is added during re-charging, how is that achieved if the workshop is not using PAO68 oil?
Chris

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Re: A/C - conversion to R134a

Post by Vanny »

Obvious open question here, what's the current state of the system? Is it currently running? Does the compressor even engage.

If you're reviving a long since stopped system then there are a lot more steps to follow.

Vacuum testing is only any good on new cars. Once a car has been in the salt for more than 3 years, you need to be doing a drop pressure test with OFN.

Pressure test then oil. And remember the old adage, fluids wont compress. If you fill your compressor with oil, then spin it over, it will go pop.

I'd take a similar line with Jaba about refrigerant volumes. 550 is a little on the low side. I'd expect 600+20cc.

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Re: A/C - conversion to R134a

Post by white exec »

Hi Vanny,
Thanks for picking this up.

The system is all there.
Sanden SD709.
Unsure when it last had gas (car bought from France last October).
If AC is switched on, compressor engages and runs, and so do the twin fans (slow speed).
Only tested this once, when mild warmth could be felt on the alu pipe entering the top of the condenser; 60sec test only.

No 'salt' - car is underside protected and rust-free. (Cavities and all else to be redone.)
Have today ordered adaptor ports (1 and a spare), new O-rings (Citroen), PAO68 oil, new dryer (Valeo).

Thanks for confirming 'pressure test, then oil'. Will fit the O-rings and dryer, and get it pressure tested.
Any recc'd lubricant/etc for the O-rings? eg silicone grease, blue hylomar?

Can you also advise on draining the old oil, with compressor still on the car - through which port/orifice?

Have now downloaded the Sanden SD Service Guide, which helps no end.

Thanks.
Chris

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Re: A/C - conversion to R134a

Post by Jaba »

If the compressor runs then you still have some pressure left in the system but not enough refrigerant to cool.
Dont forget though that the oil is not just in the compressor but all round the system too and bear in mind that pag and mineral will not mix but ester oil will. I am sure that the a/c will still work with your pag oil but it might be worth a good flush then a vacuum out before a new dryer and recharge.

You drain and fill the pump oil through the drain hole with it off the car by the way.

You might want to leave the oil change and just change all the orings yourself then take it to your a/c man to do the rest i.e. flushing, if you deem that necessary, then fitting the new dryer and recharging with gas and oil. They can do a quick vac test first to make sure all the new joints are OK.
Lube the orings with your PAG oil. The longer they can vacuum your system the cleaner and freer of moisture it will be.

My experience of aircon guys is that most of them have their own way of doing things and are not sympathetic to hands on owners like us. So have a chat with a couple first to make sure that they will do exactly what you want.

As far as gas volume goes I think you will have the aluminium condenser and will need nearer to 800cc. The 16v and TDs have a different condensor needing less volume. But your aircon guy will have tables to tell him what to put in but they may not be accurate so check with him first.

Lastly make sure that the drier is the right one cos your old and brittle a/c hoses will not like being twisted into new positions. I have a list of part numbers somewhere if you need them.
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Re: A/C - conversion to R134a

Post by white exec »

Thanks Jaba for all that really helpful info.

The new drier has its connections in exactly the same positions as the existing ones, which helps, and matches the OE pt.no.
OK - pump off to drain and (after the pressure/vac test) refill.

Will ask my workshop whether they can do a system flush, but bit concerned that the Sanden manual instructs to flush hoses, hard lines and heat exchangers, but NOT the compressor, receiver/dryer, or TXV - because "residual flushing fluid cannot be removed from these components, and they restrict the flow of flushing agent through other components". Would they really open up the system to selectively flush it?

Maybe skip the flushing, but just drain the compressor thoroughly, and rely on the PAO68's ability to tolerate any remains of the previous PAG oil?

If I've got the pump off, and the old dryer out, perhaps I can flush some of the pipes myself with some IPA (alcohol), followed by a dry off with the airline. Good idea or not?

Sorry to fire more questions; not an operation I've had to do before.
Chris

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Re: A/C - conversion to R134a

Post by xantia_v6 »

I have converted a couple of Jaguar systems, and if a "compatible" oil (one that is compatible with both R134 and the oil currently in the system), you dont need to flush the system, just drain as much of the old oil from the compressor as you can. Record (if possible) the quantity old old oil removed from the compressor.

Make sure that the operator understands compatible oils and has the right stuff on hand.

You can either dismantle and flush everything, or just change the compressor oil, I have done it both ways. I would advise doing it the easier way, as there is a chance that the hoses may be a bit porous to R134 and will need replacing anyway, so be prepared for a second round of filling.

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Re: A/C - conversion to R134a

Post by white exec »

OK, thanks Mike, that's helpful. Quite happy to take the easier route.

One question: If I refill the pump with the new oil (having done O-rings and new dryer), if the workshop then performs a vacuum test (as a test, and as part of regassing), is there any risk that some of the new oil could be drawn off, or should it all stay in there? I ask, as the single charging point is about the lowest point of the system, right under the compressor... Or would the compressor happily contain all the new oil (135ml+10% for the new dryer), without loss?

Alternative is to give them the car without the new oil in it, and get them to add it as part of the regas.
Chris

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Re: A/C - conversion to R134a

Post by Vanny »

Don't use alcohol to flush flurolined refrigeration hoses.

Done correctly, flushing of each individual component should be done using a machine and liquid refrigerant. I've done it with a Robin Air machine and all the adapters they sell and it takes days. I was once told, and have successfully used white spirit to clean out pipes.

I've always used ND8 or ND12 for oiling compressors and fitting o-rings, but I had a plentiful stock. I'm told it's rather hard to get hold of.

Drawing a vacuum over a refrigeration circuit is not like hoovering the carpet. Only gas will come out, no dirt. When the system is running the gas picks up the oil and moves it around the system, over the o-rings and through the compressor keeping everything lubricated. This means in a healthy system, when gas is vacuumed out, it will be carrying a little oil which needs topping up.

The reason for the vacuum is to reduce the boiling point of water (moisture) to below ambient temperature so the moisture is removed. 9 out of 10 times it WONT tell if or where a minor leak is. This is why the system needs pressure testing with OFN to check for leaks before vacuuming down. Any mobile refrigeration technician worth employing will know this. Garages with an automatic machine aren't much use for anything but a quick top up. I would never put leak detector dye in a car because it causes more hassle than good.

Having converted R134a cars to R1234yf and back again, you need to be slow, methodical and keep near sterile conditions. But then we where changing the whole air handling units as well to keep everything super clean.

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Re: A/C - conversion to R134a

Post by white exec »

Thanks Vanny for the additional advice and confirmation, much appreciated.
Managed to find a Mahle training video yesterday, which covered system flushing: an involved process, which required removal and by-passing of several parts of the system.
The Mahle-Behr PAO68 oil I've ordered is the version with UV dye added, hopefully not a problem.

I have a way forward now, which is always a Good Thing.
Chris

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Re: A/C - conversion to R134a

Post by white exec »

Hi Jaba,
You said there were 14 O-rings to change.
I can account for 9 of them...
.
AC O-rings _1.JPG
AC O-rings _2.JPG
Is that right, or just the #14 service pack (now NFP) ?

Thanks.
Chris

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Re: A/C - conversion to R134a

Post by Jaba »

Yes I did. The extra ones are: 4 needed for the expansion valve input and output this is in addition to the two on the diagram for the hoses and one more not shown for the drain plug. No idea about the service pack I get mine from an a/c equipment supplier in a kit of a lot more than 14 of many different sizes.
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Re: A/C - conversion to R134a

Post by white exec »

Thanks for the really quick reply.
.
Expansion valve.JPG
Any idea of size of those four?
LHD, so that will be fun.
Is replacement essential?

Thanks.
Chris