R-12 to R134

[5FistsoftheNorthStar]

Hey guys,

I was wondering if there would be any problems on this conversion.

My 91T has R12 of course and a I am swapping in a Gen3 R134. Would I just install the R134 compressor and thats it or is there some modifying I have to do to it? THanks a million!

[Justin311]

Arg. I have been dealing with my AC system for the last 3 weeks. I have a lot of information LOL, and my AC is STILL not working

Anyways, in order to change out to 134 [completely] you have to change everything except the actual lines and condensor/evap coils: Compressor, dryer, o-rings, fittings, oil. There are probably 15 o-rings in all.

NOW, that being said, many people simply pull a vacuum on the system, put some adaptor fittings on it, and refill it with R134a. This may or may not work in all cases and definitely is not the "proper" way to do it, but it has been proven to work in some cases.

If you do convert over to the GenIII compressor, please post, as I may be doing the same. The dryer is probably the hardest part to get to on a stock car, as it is right behind the front bumper. Not sure but you may be able to pull the driver's side wheelwell liner and access it.

I ran into the problem of even after the fact that I have my license (I'm an HVAC engineer, but don't know much about cars) and can get R12 replacement freon (called Hot Shot) I can't pinpoint an R12 leak somewhere in my system. They don't sell dye kits for R12 anymore, R134 dye kits are not compatible, and a "sniffer" is $200 friggen dollars. For now I'm sweating like a pig.....100* and 75% relative humidity down here

[baktasht]

Originally Posted by Justin311

Arg. I have been dealing with my AC system for the last 3 weeks. I have a lot of information LOL, and my AC is STILL not working

Anyways, in order to change out to 134 [completely] you have to change everything except the actual lines and condensor/evap coils: Compressor, dryer, o-rings, fittings, oil. There are probably 15 o-rings in all.

NOW, that being said, many people simply pull a vacuum on the system, put some adaptor fittings on it, and refill it with R134a. This may or may not work in all cases and definitely is not the "proper" way to do it, but it has been proven to work in some cases.

If you do convert over to the GenIII compressor, please post, as I may be doing the same. The dryer is probably the hardest part to get to on a stock car, as it is right behind the front bumper. Not sure but you may be able to pull the driver's side wheelwell liner and access it.

I ran into the problem of even after the fact that I have my license (I'm an HVAC engineer, but don't know much about cars) and can get R12 replacement freon (called Hot Shot) I can't pinpoint an R12 leak somewhere in my system. They don't sell dye kits for R12 anymore, R134 dye kits are not compatible, and a "sniffer" is $200 friggen dollars. For now I'm sweating like a pig.....100* and 75% relative humidity down here

I feel your pain man... new compressor, new o-rings, new condensor... vacuumed it all out... left a vacuum guage on it overnight to make sure there's no leaks (pressure loss)... filled with r134... kinda cools now... but not enough to fight 85-105 degree days....

[Justin311]

Hey Bak:

What compressor did you use, genIII?

Can you give sort of a write-up on how you "vacuumed" it all out and set up the gauge and stuff? I have all the tools (R12 gauge set, R134 adaptors, vacuum device I purchased from harbor freight, air compressor, etc) but I haven't been able to find a good writeup on exactly what I do. All I've done so far is refill with R12 replacement and it leaked out so now i'm back at step 1!

[baktasht]

Gen2 compressor...


Here is a step by step of what I did, most of it was recommended to me by my uncle who is retired bmw master mechanic.


* I replaced my condensor, evaporator, o-rings, and compressor with all new parts from toyota. in addition to the o-rings where the lines connect to the compressor I also used that copper gasket maker stuff too. I was told to use it on the flat metal surfaces that touch the compressor housing, and to NOT let it get on the O-rings when i'm applying it (some will get on them after you tighten them down). Make sure it's a very very thin layer that barely covers the metal surface. Tighten everyting down...

* Use a vacuum pump on the low-pressure side connector (on a USDM car that's the one toward the passenger side of the car). Leave the vacuum pump connected and on for about 20 minutes. Then remove it and connect a A/C pressure guage to the low-pressure port to see how much vacuum you're getting. It should be around 30 psi of vacuum. If it's less, connect the vacuum pump again and let it run, then check the pressure again until you have around 30 psi of vacuum. DO ALL OF THIS WITH THE CAR OFF AND NOT RUNNING.

* Now that you have vacuum'd your system, leave the pressure guage connected to the low-pressure side, and note the exact pressure reading. Leave it connected for about 1.5 - 2 hours (still with the car OFF and NOT running). After about 2 hours check the pressure reading. If the pressure has fallen then you have a leak in your system. If not then you are ready to fill with R12 or R134 (or substitute). If the pressure falls quickly you know you have a big leak and something is probably not connected or seated properly. If the pressure falls slowly then you have a small leak somewhere that is going to be a pain in the *** to track down (but nevertheless needs to be tracked down and fixed, otherwise the system won't hold the gas for very logn and you'll just be wasting money by filling it up).

* If you have good pressure still, and no signs of leaks. Now you're ready to fill the system up with your choice of R12 or R134. If you have a Low/High automobile air conditioner pressure guage set, then connect the HI (red) guage to the high side of your system (the connector on the driver side). If you don't have a pressure guage set, no worries...

* Take your first can of R12/R134, shake it up really good for 30 - 60 seconds. Connect your can of gas and your lines to the LOW PRESSURE side. Start the car and turn the A/C on and all the way to the cold side, and make sure the fan is on high.

* Now if you have some kind of a trigger or valve to open to let the gas flow into the system, now is the time to open it up and let the gas flow. Let the gas flow, while giving the can a good shaking about every 60 seconds. When the can feels empty disconnect the can/lines to the low pressure side. Make sure you disconnect the line first... and then the can (unless you have some sort of an on/off valve, otherwise you'll let air into the system or you'll let gas out). Now shake up the next can, and connect it... etc....

* Keep filling the system until your pressure guage connected to the low side reads around 35 psi (or the high pressure side reads around 140-150 psi). If you do not have a pressure guage set, use the one that came with your cans/filling lines. If they did not come with one either then don't even attempt this until you get at the very least a pressure guage to fit to the low-pressure side.

* So this whole time the car has been on and running, with the A/C on COLD and the fan on HIGH. By the time you get around 35psi of pressure on the low pressure side you should start feeling cold air coming through the vents. If you don't then something is wrong. Make sure the compressor clutch is kicking on when you turn the A/C on. You should hear it click on, or you should see the RPM drop/rise when you turn off/on the A/C. If this is not happening then something is wrong that the compressor clutch is not activating. And that's a whole other can of worms

[Justin311]

Nice writeup, thank you!!!

Basically what I did to fill it (I have AC gauges) but I did not pull a vac cause there was still some in the system, but apparently I have a very slow leak I have to find I guess starting with a vac will tell me how slow of a leak I have.

So, how much did all the toyota parts cost you to replace? Do you have any part numbers? I'm hoping mine is just an O-ring, but I might just replace the dryer and compressor while I've got it all apart, to update to 134.

[baktasht]

I haven't tried it yet... but it has been suggested to me to maybe try one of the R12 substitutes like:
http://www.es-refrigerants.com/produ.../3/default.asp

I don't remember the cost or part numbers, I bought all the parts about 7 or 8 months ago while I was in the process of my motor swap. I remember the only thing I had problems finding were the o-rings because the dealer had no part numbers for them. Instead they finally told me to bring in the old o-rings and they just gave me some that were the same size/thickness/etc...

[ABMR2]

Found this a couple days ago when I was pissed that I didn't have AC and that my system hadn't been retrofit but had been filled with R134.... 2 cans on 5/5/05 and another 3 cans on 6/27/05 before I bought it... needless to say, I think I'm low on refrigerant.

http://filebox.vt.edu/j/jagibbs/webp...conversion.pdf

[V6'er]

The "proper" way to do a conversion is NOT the only way.

THE reason that you have to remove all traces of R-12 in a system is because the introduction of R-134 turns the R-12 traces to glue. This is in fact, a good thing, as hoses now become sealed up, instead of leaking even more like was previously believed.

It is a myth that all of the O-rings need to be replaced. Also, the oil is the one of the biggest issues, so:

1. Do NOT EVER get a new "R-134" compressor just because you had an R-12 compressor. It's the same compressor as an R12 compressor, but it has a different oil charge from the factory. It's a simple job to flush the compressor with alcohol.

2. The same applies to the condensor and all of the other parts, except the receiver/dryer - all of the system can be flushed with alcohol (denatured). It is NOT necessary to replace major parts of the system because you want to convert it. (The residual alcohol boils out when you pull a vacuum on the system - it has a high vapor pressure.)

3. Put in the required amount of Ester oil, usually about 6 oz. This is synthetic, and is THE perfect replacement for the old crappy mineral oil (R-12) and PAG (R-134).

4. Replace the Receiver/Dryer. It's cheap, and it affects performance.

5. If you put in R-134, fill with a charge equivalent to 80% of the R-12 charge, which is 28-32 oz. for '91-'93 MR2's.

6. Your vacuum pump may not pull to 30 Inches of Mercury (not PSI). Any reasonable vacuum below 20 in. Hg. will do fine. The real trick here is to boil out any residual moisture. The greater the vacuum, the more effective the procedure.

7. Connect both manifold hoses when you get started. There's less chance of getting air into the system if you pull a vacuum through the whole system, all hoses included. (Open both manifold valves.)

8. A properly charged and functional MR2 A/C system will in fact cool pretty well with R-134. I have proof of this with a few MK2's.

9. If you really want a fluorescent dye added, get one that's Ester oil based, as it will work in almost any system.

10. Ditch the crappy R-134!!! It's molecules are smaller (so we are told) than R-12 molecules, so it leaks out faster. (This is one reason for the O-ring story - the newer O-rings are supposed to seal "better". Maybe...)

ES-12a, manufactured by EnviroSafe in Pekin, IL, is THE stuff to get. It is:

1. Non-ozone depleting
2. Non-toxic (well, not severely brain damaging like R-134)
3. Flammable (but not like propane is)
4. It's only a mail order product for most of us
5. You use less than R-12 or R-134
6. It's a petroleum product, so it's molecules are larger than R-12 and R-134 molecules, so it has less chance to leak.
7. It is compatible with almost every A/C oil out there - no need to change oil.
8. For 12 bucks, you can add a can of ProSeal to fix most small leaks.

8. COLD. No, I mean COLD. I HIGHLY recommend the Industrial ES-12a, as it gets colder than the regular version. MR2's will cycle off about 42 degrees F (measured at the center duct). My Lexus SC300 goes down to 31 degrees. The colder it gets, the more efficient it is, and the less it needs to work to get your car cold. My MR2 has will pull the duct temp up to 50 degrees below the inlet temp. R-12 and R-134 will not ever do that.

I've put this stuff in so many cars, I've gone through two cases of cans and a 30 Lb. tank.

AND, don't forget to check your heater water valve to make sure it's closing all the way. (The heater core lines should be cold to the touch.)

[baktasht]

Very very good info V6'er. I'm definitely going to vacuum out my system again. Change the dryer again and fill it with ES-12a. I'm hoping this will make things work a bit better...

[5FistsoftheNorthStar]

Wow this is all great info guys! THanks!

[ABMR2]

So if I wanted to fill up w/ ES-12, I'll need to flush my system? Do E134 and ES-12 not get along?

[V6'er]

Originally Posted by ABMR2

So if I wanted to fill up w/ ES-12, I'll need to flush my system? Do E134 and ES-12 don't get along?

ES-12a is "mechanically compatible" with both refrigerants. It's not legal in the USA to mix refrigerants, so you're simply not supposed to do it.

Better yet, why let the inferior R-134 take up the space that ES-12a could occupy? You'd have a less than optimal system, and you'd feel the difference.

You can charge ES-12a into a system with zero pressure (no vacuum) as long as you know that's it hasn't been open and has no air in it. (Air will displace refrigerant, and it carries moisture.) It is always best to pull a vacuum if you can.

And no, you do NOT need to flush your system. I would add an ounce or two of Ester oil if you could.

[alphonsus]

I think my car may have been converted to r134 when the motor was swapped. Is there a way to check and maybe convert it bcak to r12?

[V6'er]

Originally Posted by alphonsus

... Is there a way to check and maybe convert it bcak to r12?

You haven't been paying much attention here, have you?

[alphonsus]

Originally Posted by V6'er

You haven't been paying much attention here, have you?

When I got my car back after the swap, I had a r134 retrofit kit in the frunk. I don't know if they actally performed the retofit or they just left the kit in the frunk. I just needed to know when I buy the es refrigerant, will the fittings work, or will I have to remove the r134 retrofit to make it work.

[lateralG's]

Mitch, what great information! You are such a great resource, and so generous with your knowledge. Bravo Zulu!!!

[V6'er]

Ok, sorry, I didn't mean to be so harsh.

My point was that you DON'T want to go back to R-12. So, you move forward.

If you have a correctly (read, "legally") installed R-134 kit, there will be "bayonet" quick-disconnects on the ports. And R-134a cooled very well in my car, so I'm not against it at all. It sure is easy to get your hands on!

Actually, you reminded me of something that I forgot to mention about the ES-12a upfit - a correctly (again, legally) upfitted MR2 will have bayonet adapter fittings on it. You can buy these from the folks at www.es-refrigerants.com, or you favorite parts store.

I will caution you guys on this: do NOT buy the adapters with the valve stems in them. Buy ONLY the variety with no valves; these work far better. And, they are cheaper.

Remember that the high pressure side is 3/16", and the Low side is 1/4".

Also, if you have a manifold set without R-134 style bayonets, I'd just leave them off. I suspect that the legality of all of it has to do with selling your services to someone else. Failing to put them on your own car isn't exactly about to get the Feds after you.

[Justin311]

Hmm, lots more good info. Will have to check into this refrigerant, I've been using Hot Shot for years....

[V6'er]

Originally Posted by Justin311

Hmm, lots more good info. Will have to check into this refrigerant, I've been using Hot Shot for years....

I asked a friend of mine that's been in HVAC for many, many years. He said the Auto industry will just never get behind a flammable refrigerant. Is Hot Shot one of those?