www.jec.org.uk

I've read with interest the many posts under the heading "AIR CON" on the bulletin board. Quite an interesting subject I'm sure you will agree! I'm also glad to learn that most people choose to keep their air conditioning systems operational. The subject can be somewhat of a mine field. But I hope I can dispell a few myths regarding this subject starting with alternative refrigerants.

As a time served qualified air conditioning engineer with 20 year experience, please allow to to clarify a few facts regarding the various refrigerants and their properties and compatabilities. I hope this information will help you to decide which one is best for you.

R12 - Most Jaguars manufactured prior to 1992 had refrigerant R12 air conditioning systems as standard. (1992 was the recognised industry change-over year from refrigerant R12 to refrigerant R134a). R12 is a very efficient refrigerant, it contains larger molecules than R134a. R12 is made up of C.F.C's, (Chlorflorcarbons) which are extremely destructive to the Ozone Layer. That's why the manufacture of R12 was banned. At the time of it's demise, the only viable refrigerant available for automotive air conditioning applications was R134a.
As far as I am aware, it is not illegal to use R12 (I have a few Kilograms left in a cylinder) but releasing it into the atmosphere and manufacturing it certainly is. R12 is an inert vapour at atmospheric pressure. It is odorless and colourless. It is heavier than air and in very large concentrations will deplete oxygen and cause suffocation. Under pressure, it condenses into a liquid. Releasing R12 in liquid form can cause severe freeze burn to your skin. If R12 is burnt, phosgene is released which is better known as mustard gas.

R134a - is nowadays, the most commonly used refrigerant in automotive air conditioning systems for new vehicles. It is far less efficient than R12. It is not compatable with systems originally designed to operate with R12 unless an extensive lubrication modification is carried out on the system first. The use of R134a necessitates the use of synthetic (polyolester or P.O.E) compressor lubricant oil. R12 systems contain standard mineral lubricalting oil. Chemicals in R134a react with mineral oil and polymise it (tern it into a glue like substance). Therefore, you cannot add R134a to an R12 system without expensive retrofit modification.
R134a is an H.F.C (Hydroflurocarbon) refrigerant. It does not deplete the ozone layer but it does have properties that contribue to global warming (Greenhouse effect) similar to Carbon Dioxide. It is illegal to knowingly release R134a into the atmosphere. R134a is an inert vapour at atmospheric pressure. It is odorless and colourless. It is heavier than air and in very large concentrations will deplete oxygen and cause suffocation. Under pressure, it condenses into a liquid. Releasing R134a in liquid form can cause severe freeze burn to your skin.

R413a (not to be confused with R134a) also known as R49 - A company called Isceon developed R413a (Isceon 49) several years ago as a direct "drop in" replacement for R12. It is a far more efficient refrigerant than R134a which means your air conditioning system will cool and dehumidify the air more efficiently with R413a than it will with R134a. R413a It is a long term direct replacement for R12. It's chemical composition is known as an Azeotropic blend and it has a larger molecular structure than R134a. It has an ozone depleting property of Zero, therefore, it does not damage the ozone layer. It has similar global warming properties to R134a. It is odorless and colourless. It is heavier than air and in very large concentrations will deplete oxygen and cause suffocation. Under pressure, it condenses into a liquid. Releasing R413a in liquid form can cause severe freeze burn to your skin.
The best feature regarding the use of R413a is that absolutely no modifications at all are required to use it in either a system designed to operate with R12 or R134a. R413a is compatable with all compressor lubricating oils including mineral, P.O.E and alchobenzene lubricants. Therefore, it can be added to any automotive air conditioning system after nothing more than a system pressure leak check and a thorough evacuation. No other parts, materials or lubricants are required.
Refrigerant R413a (R49) is slightly more expensive than refrigerant R134a. But R413a can be put straight into any automotive air conditioning system (R12 or R134a) without modification. It is far less labour intensive to use. It is therefore, much cheaper to convert your R12 system to operate on R413a than it is to convert it to use R134a.

From my proffessional experience, R413a (R49) is a far better alternative to R134a. Both my Jaguar air conditioning systems have run on it for the past five years or so and I've been extremely happy with the results. Why pay out many hundreds of pounds to convert your R12 system to a R134a system when you can add R413a to your system without modification far more cheaply. Respect due to anyone who has already converted to R134a, but is there really any point when there's a direct "drop in" replacement for R12 which is more efficient anyway?

I recently spoke to a gentleman who paid a whopping £700 + VAT to convert his BMW 7 Series to R134a from R12. He could of had it charged with R413a for no more than £100.00 + VAT. I know which price I'd sooner pay!

Food for thought? Comments and experienses are welcome of course!

Regards,

Steve.

N.B. Please be aware - releasing any refrigerant knowingly to atmosphere is not only dangerous (can cause severe freeze burn, blindness etc) but it is also illegal.

Contrary to popular belief, it is possible top up air conditioning systems using blended refrigerants without any ill effect. Theoretically, blended refrigerants like R49 can "SPLIT" if allowed to leak. And they are supposed to be charged into the system in liquid state to prevent this happening.
However, time has prooven that the splitting effect does not occur geatly enough to effect the operational characteristics of the refrigerant.

More importantly, it is actually illegal to add refrigerant to a system knowing it has a leak. Therefore, no air conditioning system should ever be topped up. The correct proceedure is to fully decant the remaining refrigerant from the system via the use of a proper reclaim unit and cylinder. The reclaimed gas charge should be weighed in order to establish how much of the original refrigerant charge has been lost. The system should then be pressurised (to about 20 Bar or 300 psi) with Oxygen free Nitrogen in order to observe a pressure drop. The severity of the leak will be indicated by how fast the nitrogen pressure decreases. Once a pressure drop has been observed, a thorough leak detection should be carried out. Once the leak or leaks have been found and repaired, a final pressure test should be carried out.
Once the system is leak tight, a thorough moisture evacuation should be performed via the use of a vacuum pump to ensure the internal air conditioning circuit is free of moisture (including the compressor lubricant).
Only then can the system be legally recharged with a suitable refrigerant.

Thanks for an interesting write-up Steve, although still using R12, I'm sure that the day will arrive sooner rather then later when I need to address the problem.

You may be able to answer a question I have regarding refrigerant blends, that is when a system is liquid charged, surely some refrigerant would end up in the compressor in liquid form. As it is a compressor not a pump, and everyone seems to agree that a system should never be topped up in a liquid form, what's to prevent the compressor slugging during start-up? Same problem with the oil that circulates I suppose. I've no doubt there is a simple answer, but I can't work it out.
Pop

Thanks for an interesting write-up Steve, although still using R12, I'm sure that the day will arrive sooner rather then later when I need to address the problem.

You may be able to answer a question I have regarding refrigerant blends, that is when a system is liquid charged, surely some refrigerant would end up in the compressor in liquid form. As it is a compressor not a pump, and everyone seems to agree that a system should never be topped up in a liquid form, what's to prevent the compressor slugging during start-up? Same problem with the oil that circulates I suppose. I've no doubt there is a simple answer, but I can't work it out.
Pop

Hi Pop rivet.

There is a fairly easy solution to your query and thanks for asking. You've raised quite a valid point here and you are right to state that a compressor should never pump liquid as a liquid won't compress!

When charging an air conditioning system in liquid state, you must ensure that you don't slug the compressor with liquid. This can be done as follows:

A) As I've already stated, a system should only be charged after it has been fully leak tested and evacuated. Therefore, the system will be holding a negative pressure (vacuum). Before running the engine and compressor, quite a large proportion of the refrigerant charge weight can be "sucked" into the system as the refrigerant held in the cylinder will be at a pressure of 150 psi or so (depending on ambient temperature). This method is known as "drop" or "bomb" charging. As the liquid refrigerant enters the system at a lower pressure, the refrigerant will change its state and boil off to vapour. Therefore, no liquid refrigerant will be present in the system at the point of switching on the compressor. The refrigerant charge should be fed in through the high pressure (liquid) side of the system. Therefore, all the refrigerant has to pass through the metering device (expansion valve) and evaporator before returning to the compressor. You can drop charge through the low pressure (suction) side of the system but I always ensure the engine has been thoroughly warmed up first. The higher temperature in the engine bay ensures all liquid refrigerant entering the system boils off quickly.

B) It is very unlikely that an entire refrigerant charge weight will enter the system by being pulled in through a vacuum. The system and refrigerant cylinder pressures will equalize before this happens. Therefore, the remaining charge weight has to be added through the low pressure (suction) side with the system operating. All systems should have a suction accumulator built into them as standard. This will act as a catchment vessel for any liquid returning to the compressor. However, it is possible to liquid slug a compressor if you're not careful. This should be avoided at all costs for obvious reasons.
When liquid charging the system whilst it is operating, the refrigerant has to be metered into the system. This slows the refrigerant flow entering the system and therefore allows it to vapourize (boil off) before it enters the compressor. There are charging rigs available that will perform this operation for you. However, it's just as easy for an experienced air conditioning engineer to perform this process through a standard gauge manifold.

All systems should be charged via the correct weight of refrigerant, never through operational pressures. System pressures can vary considerably compared with ambient temperature. Many manufacturers publish theoretical system pressure readings compared to various ambient temperatures. These should be only be used as a guide once the system has been fully charged with the correct refrigerant weight. If the actual pressures measured mimic the theoretical ones, the system is healthy and functioning well. If they don't match, it is very likely that there is a restriction, air in the system or a faulty expansion valve etc.

Hope this helps!

Kind regards,

Steve.

Nice posting XJ-Steve, very thorough and well researched. I notice also there's some newer refrigerants out now, I think they're called IS24 or something. And I just found some real R12 on ebay 130029262656 !


N.B. Please be aware - releasing any refrigerant knowingly to atmosphere is .....<snip>...... illegal.
Just thought I'd add something, I used to quite a few years ago top up with 'aerosol freezer spray' in a can as refrigerant, it costed less than couple quid a 400ml can, it was pure R12 and I just sprayed in a can (via a a special adaptor I made up) every month or 3.! The really neat thing about using aerosol freezer spray in a can was that it was fully intended to be vented into the air, so I wasn't breaking the law Nowdays when you buy freezer spray in a can, it's R134a/dimethyl ether, costs about a tenner a kg and still made specifically for venting it straight out into the air!

So do I detect a legal loophole here ? - to top up leaky R134 systems without breaking the law?

Steve,

Tks very much for the info - Hugely informative. Aircon issues do seem to be figuring more and more with owners as our cars get older. I'm sure that you may now start to receive more queries as a result of kindly sharing your expertise on the Forum!

You make a really interesting comment about the illegality of topping-up systems. I suspect that nearly every car that has its aircon recharged by a garage will have had some depletion of the original content. Does that imply that technically they are all breaking the law or is there some flexibility that x% is allowed for top-up purposes? I once had a BMW which was apparently missing 70% of its refrigerant according to the discharge printout and the dealer happily refilled it with the correct amount!

Your thoughts would be appreciated and once again, tks for your contributions.

Paul Sinnott
XJS Registrar
Jaguar Enthusiasts Club

Couple more R-12 drop-in refrigerant facts to share.

R-406 (GHG) = R22 / R-142 / Isobutane The '22 and '142 blended to get the pressure curve the same as '12, isobutane to carry the mineral oil. Has a glide which increases active area of heat excahngers. Interim refigerant, being phased out, can still get it special order from A-Gas but not around much longer. About £12(TBC) per kilo. Best performing in my experience.

Blends of the above = variations of blend , not covered.here, not available easily in UK.

R-409 (aka FX56) not to be confused with R-49. R22 blend with isobutane again, another interim refrigerant. More easily available, but being phased out. £21/kilo from Climate Centre chains


Recent:
RS24 (Refrigerant Products Inc) = 'trade secret composition' but is widely beleived to be 98% R-134a, plus butane to carry mineral oil. down to £10 / kilo now

For comparison: 13.6kilo R-134a about £5/kilo on ebay, £15/kilo from Climate Center

If you buy 'top-up' R134a (containing UV dye) in a can it's £32/kilo (£26 without dye)

Very interesting comment about topping up the system and particularly so since I noticed Halfords now sell DIY kits.

I need to investigate my own this weekend since it has stopped producing cold air. This seems to have coincided with the first cold snap and the fact the wife insists on having the heater turned up. I’m hoping this is down to a sticking heater valve since these are prone to failure. Any one experience anything similar?

Nick

As R134 can now be bought at Halfrauds for 'topping up', can R49 also be legally bought without a refrigerant handling certificate?
A friend retired from the commercial A/C industry last year and has offered me his old kit including recovery unit, gauges and vac pump etc. Unfortunately his tickets have run out and he didn't keep any gas. I am fully aware about not releasing gas into the atmosphere etc. I don't want to miss out on the kit but there wouldn't be any point if I can't get the R49.
If a certificate is needed, maybe it would be worth me doing an evening course.
Pop

Pop
Excellent News..Go for it, perhaps a new door has opened for you
DH Dove

I've got a siezed compressor and so am going about getting it fixed. Being an R12 system, I've got to address that too. Having read this, R49 seemed to be the answer, but neither of the two local air con specialists knew about R49 and my local Jag dealer has "never done an R12 -> R134a conversion".

Is R49 still around? One mechanic asked if it was a domestic/industrial refrigerant(!?)

The procedure of the two specialists was; a/ decant off old R12, b/ replace top-up valves, c/ replace compressor and receiver dryer, d/ check for leaks, e/ fill with R134a.

Is this sensible? Won't there still be mineral oil (soon to be goo) still in there or is that taken care of by replacing the compressor?

Dave,
I think that with the compressor removed, most of the old mineral oil will be out of the system, as most of the oil resides in the compressor.
I changed to 134a from R12 about 3 years ago when the compressor blew a seal.
I removed the compressor, drained the oil, flushed with PAG oil, fitted an R134a compatible seal, added the correct amount of PAG oil, refitted compressor, fitted new reciever dryer and gauge/filling valves, and had the system charged with R134a, no prolems since.
I have since learnt that to make the sytem work more efficiently, a different expansion valve is needed. I now have one of these, and thats a project for next week. Its going to be a b*gger to replace due to the location that Jaguar decided to fit it

Nigelsly

You're not wrong, replacing the expansion valve is not a job for the faint hearted.
My 3.6 coupe needed a new one which (after I'd taken a look at it) was fitted by air-con specialists, they charged me four hours labour, inc recharge, test, etc. and said they didn't want to do another one

NB What exactly do you do with that pig-tail curly bit? I think it senses the temp. in the evaporator and wraps around something to stop it freezing? Also various other bits of insulation etc to get in there at the same time. Just to add to the fun the old ones can break on the way out, leaving bits inside.............

I think it's a bit like trying to get a ship into a bottle, whilst bent double over a vaulting horse

Just thought I'd cheer you up.........................

Good luck
DH Dove

Thanks for those words of encouragement!!.
The pig tail thingy fits under a small clamp, which is very difficult to access. Its also covered in some gloop, which is meant to insulate the sensor from engine heat. Need to remove thay gloop(sticky black stuff) to access the clamp.
I've got a set of flare nut spanners which hopefully will make the job a tad easier, but wont know until I have a go. It must be doable, as other shave done it, but its going to be real awkward

Nigelsly

Hope all goes ultra-smoothly for you.

I do hope you come back and report that you wonder what all the fuss is about

DH Dove