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Converting aircon on 1993 XJ from R12 to R134a

br1anstorm

NAXJA Forum User
Location
United Kingdom
I have a 1993 XJ 4.0 litre. The a/c system has been empty for about a year after the condenser (or a hose connection to it) developed a leak. My plan was - and is - to overhaul and convert from R12 to R134a.

I have been stirred into action by the fact that my radiator has just suffered a leak too. Since I have to replace that, I thought I'd do the a/c at the same time.

I've read several threads on the conversion process. I know the system has to be cleaned and flushed. But a few questions remain unanswered.

1) what parts to replace? I have new condenser and new receiver/drier. I hope and believe I can continue to use the original compressor. Do I have to replace the expansion valve as well, or can I get by with the existing one?

2) hoses (aka "lines"). There are four. I plan to replace the two that connect to the condenser, because on the old ones, the alloy-pipe sections by the radiator and condenser are pretty rusty. Can I retain and re-use the other two lines, which connect between the expansion block and, respectively, the compressor and the receiver/drier?

3) hose options. There appear to be different part nos for the hoses between 1993 models (in which R12 was used), and 1994 models (the year R134a was introduced). The latter are the same 'shape' but a couple of them have connectors or valves fitted like spurs. Will the 1994 parts fit my 1993 vehicle? And are these 'spur' connectors specifically a feature of R134a installations?

4) compressor connections. There appear to be valves on the top rear of the compressor, with what look like open/close controls. I found an old thread here in which ParadiseXJ and 90xj06 sort-of explain how these work. They seem to be rather peculiar, with three positions. Does the system have to be recharged via these valves, or via the 'new' valves/connectors on the new hose lines?

5) draining the compressor, and oil change. R12 systems use mineral oil. I believe R134a systems use a different oil (PAG?). How exactly to flush or empty the compressor? Is it necessary to de-mount it and have the oil pour out of the hose-connector sockets? Or does the oil have to be sucked out somehow, or the compressor purged using compressed air or something?

6) capacity/amounts. I haven't yet checked how much refrigerant or oil is required. I read somewhere that for R134a you need a bit less: about 80% of the amount of R12 . And how much of the new (PAG?) type of oil?

Those are the questions that have occurred to me so far. Answers, and any other wise advice, would be appreciated!
 
Hi, I'm sure you could replace a few parts and get that R12 system running good again, R12 & substitutes are still available on line, seems like a lot of
work and expense to change the system to 134, condenser, evaporator, compressor, lines and electrical rewiring not to mention new hi / low cut out switches and possibly the interior control head, also if the PCM controls compressor clutch cut in /cut out you will have to have your PCM reflashed, I have a 1988 Grand Prix that still I still run R12 in, Just bought a case of R12 12 oz cans and some compressor oil about a year ago, and all the parts for your R12 system are still available, I would definitely calculate the cost & aggravation of converting. Just a thought.
 
I’ve converted without doing anything really Redneck style.
The way it leaked there wasn’t any oil to worry about. Used the conversion kit including oil recharge after vacuuming it down.

Doing it somewhat right I, had a new compressor, new condenser, new lines, old evaporator because I didn’t feel like pulling the dash. Used pag oil for the compressor filled to specification. Vacuum it down for at least and hour, let it sit, check for leaks,then Recharged with 134a.
I believe I used a newer Cherokee condenser with 134a, although most components sold today are usually tolerant of either refrigerant


Sent from my iPhone using Tapatalk
 
Thanks for those quick replies. Just a few clarifications....

I'm in the UK. R12 is illegal and has been unavailable for years. Not even online. I did have a small cylinder of R12 which I was using to top up the Jeep and another car which had R12. There is probably enough still there for a recharge. But effectively using R12 for a/c in cars is now obsolete. And since I have to replace the condenser anyway because it leaks, I figured that now was the time to convert rather than eke out my residual R12 on just one more refill.

There are no readily available "kits" over here for a quick 'n' dirty alternative fill with some weird alternative Frosty-freez kind of stuff. Never heard of R290, and I'm definitely not going to mess with propane. I am going to convert to R134a: decision made.

I just want to do whatever is reasonable and sensible that will enable my system to run on R134a. The questions in my OP are essentially about how to achieve that. I am not about to dismantle the dash to get at the evaporator and replace it. And since the Jeep is already 25 years old I'm not expecting state-of-the-art perfection. I just want to ensure the system doesn't seize or clog up because I have overlooked some significant step.

The list of questions I asked tries to break it down into the essential practical steps. Any advice on the specific points I raised would be very welcome.
 
you will have a headache trying to make new lines work with the old compressor. the lines are diffrent and are routed diffrent. iv'e had two 94's, one must have been a pre 94 production due to it having r12. the second was r134. the compressors are diffrent and so are the lines length and routing.
you will have less headache by replacing everything under the hood.
 
You should be able to use the factory lines you have now if they are not leaking, shouldn’t have to update everything. When I put new compressor and lines they were factory exact replacements for 91-92, no re routing the lines.
The condenser was different for oem I’m not sure if I ordered a newer year or if it was just how the aftermarket replacement came, it bolted up to the same place and connected the same.
I forgot to mention you’ll need a new dryer (aka receiver) . Wouldn’t be bad to see if there some sort of ac line cleaner available to blow out any metal shavings and old oil, especially out of the old evaporator in the dash.

On some years it may be a pain to source parts. I’ve never done the job trying to update the line and compressor to 97 up components designed for r134a, I just used what was designed for the year car I was working on.

It’s not going to be as cold as the r12 but it’ll be cold.



Sent from my iPhone using Tapatalk
 
93 is the first federally mandated year for R134A, should be setup already. Just need to replace the drier and any damaged parts

If its actually R12 system then all you really need is to install adapters on the fittings (remove the shrader valve core from the originals first), replace the drier, and use Ester oil for lubricant (not Mineral Oil or PAG).

On my 91 I also replaced some of the lines to clean up the engine bay. Currently running 93 lines with the fittings welded on the compressor lines, and a custom line that goes under the battery tray instead of along the fender wall. Also replaced the compressor with 93 style, since the hose ends were different.
 
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Some vehicles didn’t get r134a until 1995. I know 94-95 was the first year for Honda, Toyota, Mazda, and many others because it was a difficult looking parts up for those vehicles, sometimes we’d need to go look at the vehicle to be sure what the customer had. My repair data says 1995 for the Cherokee. Which could be wrong.

I think the manufacturer conversion depended on how the vehicle was classified and how many r12 parts the factory ordered for production.
Also many of those first r134a cars sucked cooling. Manufactures did half assed attempts on current models, with new models actually seeing the cooling designed to work best with r134a.


Sent from my iPhone using Tapatalk
 
I completed the same conversion on a '90 XJ. Here are some observations:

1) The hoses are reported to have different internal coating. The old ones will work but will seep over time and may require recharging every couple of years. I simply pulled a set of good hoses off a '95 XJ in a junkyard. If you choose this route, the new hoses will include the proper Low Pressure/High Pressure valves for R134 and thus will connect to a normal AC pressure dial kit. If you go with the existing cables, you will need to add some R134 adapters to the ports on your compressor. Something like this will work: https://www.ebay.com/itm/R-12-to-R-...ash=item3aefc80abe:g:qisAAMXQeKNTPbNT&vxp=mtr


2) Try to find a Parallel Flow condenser. This style dissipates heat better. The one at the link below will work well but may need to be fitted: https://jeepair.com/condensers/14-x-20-universal-superflow-condenser.html

3) Don't forget to replace all of the seals - the version for R134 is reported to be different. These are available as a kit from Jeepair.com

4) Jeepair.com will also sell you a high quality PAG oil (PAG46).

5) Flushing is pretty easy but is easier if you have the compressor removed. Not sure if you can buy this in the UK but in the US you can buy a pressurized can of the proper stuff (like this: https://www.oreillyauto.com/detail/...ounce-a-c-system-flush/ca1/4384840?q=AC+flush). It generates enough pressure to push all the old oil out of the evaporator and/or the compressor.

6) The existing expansion valve and evaporator will work and will probably be good enough for the UK. I actually bought a new expansion valve for a '95 but found that the output orifice was smaller than the connection on my R12 based evaporator so I had to use the original part from the '90. The only issue this creates is that R12 and R134 have different expansion rates so for a "perfect" transition, they should be sized properly. In my case, since I have an R12 evaporator/expansion valve, my high pressure/low pressure measurements will never line up with the optimum values. For example, at 80 degrees Fahrenheit, you should see a low pressure reading of 40-45 lbs and a high pressure reading of ~150 lbs. Because of the mismatched parts, I get 30-40lbs on the low side when I have 155lbs on the high side so I don't get the perfect temperature drop. You can kinda get around this by over-charging a little and can get a nice cold output but it won't be as cold as a properly sized system.

Most of the hard stuff to find is available from JeepAir.com. Hoses are the hardest to find so a good junkyard is often the best answer. Also, it is VERY important to change out your drier when you make these changes. Since yours has been open for over a year, the existing on is going to be saturated.

As noted, make sure to run a good vacuum on the system. I use one of these and it seems to be good enough: https://www.harborfreight.com/air-vacuum-pump-with-r134a-and-r12-connectors-96677.html

I also use a gauge set from the same company: https://www.harborfreight.com/ac-r134a-manifold-gauge-set-62707.html

Last, if you want to fill with R134 from this manifold set, you will also need one of these to pierce the can: https://shop.advanceautoparts.com/p...VCYvICh0jFQtHEAkYCSABEgKjt_D_BwE&gclsrc=aw.ds

HTH
Todd
 
Thanks, Todd, for all that helpful advice. Since my original post I've moved things forward a bit.... but the job is not yet done.

In terms of parts, I can tick several but not all of the boxes. I have a new condenser, and it's a parallel flow one. I have a new receiver/drier too, as I knew that was crucial. I don't have a new expansion valve block (I hope to get by with the existing one) and I sure as h*ll don't have a new evaporator core (I don't even want to think about accessing, removing and replacing that!).

I plan to continue to use the original Sanden compressor since I assume that will be fine providing it is flushed of the old oil. I have removed the compressor, but it has no drain plug and I can only get a thimbleful of oil to drip out of the hose-connector ports. It also seems to have strange 3-position valve connections. I'll comment on hoses later....

This won't be a total DIY job. I have an engineer friend who fortunately has all the necessary equipment (gauges, vacuum pump etc), assorted O-ring seals and a stock of R134a. I'm hoping he already has the spray-stuff to flush the system - if not we'll have to source something over here in UK - and the PAG oil.

Which leaves the vexed question of hoses and the adaptors/connectors. Boy, have I had a nightmare trying to figure that out! With no ready supply of junkyard jeeps over here, I have no option but to trawl the parts-manuals, online sites like Rock Auto, and that famous auction site.... Jeepair seem to be good, but their site doesn't even list parts for the 1993 XJ, presumably because that was the transition year between R12 and R134a so there is no single set of replacement hoses.

My search has been bedevilled by the multitude of differing part numbers, the apparent changes of parts for different model-years, and (not least) the confusing tendency to use different language. I still haven't nailed the exact differences between "suction" line, "discharge" line, and "liquid" line.

It is clear from my Jeep that there are four hoses, and the 1993 parts manual gives the part numbers:

  1. compressor to condenser (discharge?): OEM p/n 5600 4350 - has no extra valve/connector;
  2. rcvr/drier to condenser ("suction"): OEM p/n 5600 4839
  3. compressor to evaporator: OEM p/n 5503 5886
  4. evaporator to rcvr/drier (a thinner hose) : OEM p/n 5600 4378
So far I have managed to source....

for (1) a 4 Seasons hose p/n 56279, which has no extra connector/valve welded on to its tube, and I also have a UAC 'discharge' hose 10049C, which is the same, but has such a connector;
for (2) I have a new UAC hose labelled a 'liquid line' with p/n 11291C;
for (3) I have a new 4 Seasons hose labelled a 'suction' line, p/n 56278, with no connector/valve on its tube;

and for (4) I have not yet found a replacement..... the hose I bought thinking it was the right one, UAC 10064C, doesn't seem to correspond to any of my current hoses, is labelled a 'suction' hose, has an extra connector valve, and looks like a shorter version of (3).

So we're going to have fun figuring out which of the new hoses to use. Depending on whether we use the hose(s) with the extra connector/valves, we may need to work out whether, and where, to fit the R12-to-R134a adapters.

Further comments (if any) will be welcome. I may post the next instalment of the story once we have taken the next steps in this operation.....
 
To try to clarify (and confirm some of your findings). I should caution that I am NOT an expert but this is what I was able to gather through research and implementation of the change-over on my '90 XJ.

AC systems flow from: Compressor -->Condenser-->drier-->expansion valve-->evaporator-->expansion valve-->Compressor

Since the expansion valve mates to both ports on the evaporator, simply think of them as one unit.


1) The "discharge hose" is the "high pressure" line that runs between the compressor and the condenser. It forms the first connection in this path. The R134 version will have a valve installed as a "T" usually with a red cap (but again, don't get caught up in the color). This "T" connector is connected to a gauge to measure the high pressure side of the system. Jeep Air part number: 72-5521

2) the "liquid line" is the line that connects the condenser to the drier. It forms the second connection in this path. This should be mostly a metal hose with a small rubber section to give you the ability to align it with the drier. Jeep Air part number: 72-5572

3) The next hose connects the drier to the expansion valve. This is also called a "liquid line" but will be designated as a "drier to evaporator" line. This one is the hardest to find. This hose is also primarily rubber with metal ends. I have never found an R134 version of this but the Jeep Air part number for the R12 version is: 27-5552. The R134 version should look similar if you can find it.

4) The "suction hose" is the "low pressure" line that runs between the expansion valve and the compressor and forms the third connection in this path. The R134 version will have a valve installed as a "T" usually with a blue cap (but don't get caught up in the color). This is the connection that is used to measure the low pressure side of the system and is also the line that is used to add R134. Jeep Air part number: 72-5553

The hoses used in the R12 system are the same size and connectors as those used on the R134 system from 1994 until 1996. After 1996, Jeep moved to the compression type fittings that require a special tool for removal. As such, where possible, source hoses from a 1994-1996 series XJ and you should be alright. This fact also partially explains the wealth of part numbers out there. The way I visualize it is this:

1988-1996
There are two versions of every hose: R12 and R134 but the connectors are identical. This makes a DIY conversion possible.

After 1996
Different connectors are used and thus, is not a DIY job to convert.

As I noted below, there is a difference in the molecular makeup of the rubber sections of an R134 hose but physically, they will look the same as an R12 hose. The only visible difference are the two hoses that have the "T" fittings for the gauges on the R134 system.

If you don't change the evaporator, then you shouldn't change the expansion valve. As I noted below, the R134 expansion valve looks identical to the R12 version but the connection between one of the ports on the evaporator is a physically different size and will not mate.

I included the Jeep Air part numbers above so that you can look at the pictures on the web and compare them to your hoses. They should be VERY similar in length and the connectors should be identical.

HTH
Todd

Thanks, Todd, for all that helpful advice. Since my original post I've moved things forward a bit.... but the job is not yet done.

In terms of parts, I can tick several but not all of the boxes. I have a new condenser, and it's a parallel flow one. I have a new receiver/drier too, as I knew that was crucial. I don't have a new expansion valve block (I hope to get by with the existing one) and I sure as h*ll don't have a new evaporator core (I don't even want to think about accessing, removing and replacing that!).

I plan to continue to use the original Sanden compressor since I assume that will be fine providing it is flushed of the old oil. I have removed the compressor, but it has no drain plug and I can only get a thimbleful of oil to drip out of the hose-connector ports. It also seems to have strange 3-position valve connections. I'll comment on hoses later....

This won't be a total DIY job. I have an engineer friend who fortunately has all the necessary equipment (gauges, vacuum pump etc), assorted O-ring seals and a stock of R134a. I'm hoping he already has the spray-stuff to flush the system - if not we'll have to source something over here in UK - and the PAG oil.

Which leaves the vexed question of hoses and the adaptors/connectors. Boy, have I had a nightmare trying to figure that out! With no ready supply of junkyard jeeps over here, I have no option but to trawl the parts-manuals, online sites like Rock Auto, and that famous auction site.... Jeepair seem to be good, but their site doesn't even list parts for the 1993 XJ, presumably because that was the transition year between R12 and R134a so there is no single set of replacement hoses.

My search has been bedevilled by the multitude of differing part numbers, the apparent changes of parts for different model-years, and (not least) the confusing tendency to use different language. I still haven't nailed the exact differences between "suction" line, "discharge" line, and "liquid" line.

It is clear from my Jeep that there are four hoses, and the 1993 parts manual gives the part numbers:

  1. compressor to condenser (discharge?): OEM p/n 5600 4350 - has no extra valve/connector;
  2. rcvr/drier to condenser ("suction"): OEM p/n 5600 4839
  3. compressor to evaporator: OEM p/n 5503 5886
  4. evaporator to rcvr/drier (a thinner hose) : OEM p/n 5600 4378
So far I have managed to source....

for (1) a 4 Seasons hose p/n 56279, which has no extra connector/valve welded on to its tube, and I also have a UAC 'discharge' hose 10049C, which is the same, but has such a connector;
for (2) I have a new UAC hose labelled a 'liquid line' with p/n 11291C;
for (3) I have a new 4 Seasons hose labelled a 'suction' line, p/n 56278, with no connector/valve on its tube;

and for (4) I have not yet found a replacement..... the hose I bought thinking it was the right one, UAC 10064C, doesn't seem to correspond to any of my current hoses, is labelled a 'suction' hose, has an extra connector valve, and looks like a shorter version of (3).

So we're going to have fun figuring out which of the new hoses to use. Depending on whether we use the hose(s) with the extra connector/valves, we may need to work out whether, and where, to fit the R12-to-R134a adapters.

Further comments (if any) will be welcome. I may post the next instalment of the story once we have taken the next steps in this operation.....
 
It just hit me that the UK will be a right hand drive system. This means you may have parts that are a mirror image of the pictures I shared. My, this does get complicated, doesn't it?:gee:
 
Also, your existing compressor should be fine. As noted below, people in the US routinely convert to R134 and the compressor doesn't need to be changed.

One last comment, the drier has 3 connections. The two hoses will be obvious but the third is for the pressure switch that signals the compressor to turn on. You can move the switch from your R12 drier to your R134 drier and it should be find but make sure to change the seal.
 
Todd, as with your previous posts, that latest info is hugely helpful.

Just to set your mind at rest on one point - my Jeep is a stock US-spec, LHD vehicle. Long story short, I bought it new as an 'import' in 1993 (from a Belgian agent who I guess mainly supplied US Forces personnel in Europe) because I needed an LHD to take out to my work in the Middle East and the Jeep dealers in UK couldn't, or weren't allowed to, sell LHD models. Brought it back to UK a decade later, and have continued using it ever since. So that's why I'm reliant on Rock Auto and US suppliers for anything beyond routine replacement parts, and hang out on NAXJA forums rather than any UK online networks.

Thanks also for that brilliant, simple, straightforward guide to hoses and their descriptions. I reckon I'm just about there. All the new hoses seem to have the standard connectors at each end so no special tools needed. The only new hose I haven't got is the hard-to-find drier-to-expansion-valve one. I think I'll just have to re-use the original. I have a new discharge hose with the T-valve for the high pressure connector, but unfortunately the new suction hose I have doesn't have the T-connection for the low pressure connection. Hope my engineer friend can figure out a solution to that.

To correct a small error in my previous post: the compressor does have a drain plug and I have drained what oil remained. I will indeed re-use that compressor. Also noted the drier connections and switch, and will be replacing all the seals I can find!

My Easter weekend schedule is now clear: long hours in the garage.... Well, it's all part of life as an XJ owner!
 
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