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R12 to R134 conversion

Floridaman

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May 26, 2021
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Parts are like 250 bucks to convert, has anyone done one? Sounds easy. I know about having to vacuum the system.
 
What is the vehicle?
Many ways from fuck-it to money pit.

Parallel condenser, retro oil, don't overfill. Maybe hoses.
 
Another option is the AG/Aero version of R12a can be used minus the whole 134 conversion.

Quoting...

last week I replaced the compressor on my 92 Astro van (still was running R12), and instead of converting to R134a, I put in an alternative refrigerant called R12a. I bought the stuff at the Farm Machinery Show in Louisville last winter because some farmer friends told me that it works well in their tractors and is much cheaper than R12. It works as well as the R12 did as far as I can tell, but you have to be careful to put the conversion sticker (included in the case) on so someone else won't mess up later. It only uses about 1/3 as much material as the original in actual weight, but each can only contains about 6 oz. of the stuff, so it's no big deal. I am told it is less likely to leak because its molecular makeup is larger. It cost me $5 a can, which is pretty close to the price of R134a, and I didn't have to do any oil changing or messy flushing. I am very happy with it, you may be too. Here is the website for the manufacturer.
www.duracoolusa.com
 
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The hardest part from what I remember is making sure the system is completely flushed of the old oil. R12 oil causes all kinds of fun in a R134 conversion.
 
The hardest part from what I remember is making sure the system is completely flushed of the old oil. R12 oil causes all kinds of fun in a R134 conversion.
It it and harder than sticking a vacuum pump on it and coming back hours later?
 
I had an 92 Cavalier as my first car. There was a leak somewhere in the system and the R12 leaked out. Ran it without A/C for years and one summer I got annoyed with being hot, I said Fuck it and I just bought some 134a with the stop leak additive and the adapter fitting. Filled that bitch up and had A/C again. Figured the worst thing that would happen would I seize up my AC compressor and I would have to replace it anyway. Worked for a couple years then I sold the car with working AC.
 
It it and harder than sticking a vacuum pump on it and coming back hours later?
The only time I did a conversion was back in the late 90's. Vacuumed it out then replaced the filter dryer, orifice tube, rubber hoses, some gaskets. Vacuumed again and finally refilled with R134. Unfortunately it stopped working due to the orifice tube being clogged from R12 oil still in the system. So started over flushing the system first and replaced the filter dryer again. After that, no issues.

Not a professional here, only relating my experience. So yes, I found flushing the system to be the hardest part.
 
I've converted two 80s Toyotas, an 80's Mustang and a DeTomaso Pantera to R134. It's not super hard - but you can't take shortcuts.

  1. Mineral oil and R134a don't mix.
  2. Flush the entire system (pump, condenser, evaporator, etc)
  3. Replace the Drier
  4. Replace the expansion valve or orifice tube (depends on the system)
  5. Replace all o-rings and inspect all the lines. The rubber lines and the condenser are the most prone to leaking. Condenser is usually due to rock damage.
  6. Vacuum purge the system
  7. Fill with R134a

Here's a quote from another thread that I posted a how-to on an FJ60
I just did the A/C on my FJ60 (which blows ICE cold now BTW). There's a right way to do the A/C, and there's a WRONG way. What you are proposing to do is the wrong way. It seems like a lot of steps, but if you do it right, you only have to do it once and even purchasing the tools you will still be money ahead. Plus I've done something like 10 cars for people, it's a good way to make some side cash. For reference, I am not an ASE Air Conditioning Technician.

If your A/C stopped working, 99% chance you have a leak somewhere. Most of the other parts like compressors and expansion valves are pretty resilient over time. Putting more refrigerant in it is merely wasting refrigerant. Also you never refill any A/C that has had its drier/accumulator exposed to the atmosphere for more than a few hours, because this will cause your A/C to ice up internally and not work. This is because the Calcium Carbonate in the drier will become saturated with the moisture from the air and no longer remove the excess moisture in your A/C system. You'll notice that new driers are shipped vacuum sealed, and that you have to vacuum purge the system. The reason you do this is to remove as much moisture as possible before adding refrigerant.

The standard rubber o-rings of an R12 system will not stand up to ester or PAG oil from the R134a and will all have to be replaced, so now is the perfect time to take the extra hour or two and replace all those fittings.

You need to take the A/C evaporator out of the truck, which is not hard in an FJ60 since they do not require removal of the dash to take out. You will also need to buy A/C flush to flush the R12 mineral oil from the Evaporator, lines and Condenser. I used Acetone, but I did all of mine off the vehicle in a well ventilated area and let them air dry for a few days. You can use compressed air to speed this up, but remember that solvents are explosive when put into vapor.

Keep in mind I just did this to a rather custom system within an FJ60 (involving a Ford V8 and ECU). It's really not that hard or time consuming.

What you'll need:

Steps
  • Remove and inspect ALL existing hoses and connections
  • Clean all hose ends with scotch brite or light wire wheel to ensure they are smooth
  • Replace ALL o-rings including those for the outlet of the pump. The pump outlets are held on by 2 6mm hex head allen screws and take two 15mm o-rings per side.
  • Flush condensor and evaporator
  • Replace expansion valve in evaporator, making sure to lubricate o-rings generously before reassembly.
  • Re-install evaporator in truck, hook up discharge line (the big one) and slowly pour half of the required oil into the large tube before hooking it to the suction side of the compressor. The hoses are different sizes so you can't really screw it up.
  • Pour the remainder of the oil into the condenser.
  • Install new drier/accumulator (pass side of the radiator)
  • Install all hoses with new o-rings (generously lubricated) and tighten. Be sure not to overtighten these fittings.
  • Install retrofit fittings on both sides of the system.
  • Hook up manifold to appropriate quick connect fittings. Hook up vacuum pump.
  • Turn on vacuum pump, open both red and blue valves and observe the gauge on the blue side. It should read between 20-30 in Hg. Let run for 20-30 mins. You do this to remove all moisture. It's not uncommon to see water vapor flow like fog from the vacuum pump. That was previously in your A/C lines.
  • Close both valves. Turn off vacuum pump. Let system sit for 30 mins.
  • If it holds vacuum, you're ready to fill it.
There's a bunch of youtube videos on this that will probably be much more beneficial than my wall of text. EricTheCarGuy has a really good explanation of how to do it.



I know that's a long post, but there are ways to do air conditioning that will not cost you $1500 at the A/C shop and will not cause you to leak all your refrigerant to atmosphere.
 
Everything A/C is a trade secret, you are not supposed to know anything or ask questions.

There are many debates on the 'right method', especially flushing.
When I did mine, I found this forum.
They have a sticky for 134 conversion...

I also made enough trips to local AC parts place and got some real world advice from owner who has been doing it for 30-40 years.

My 1972 ford was still R12 but already had a sanden pump and a parallel flow condenser. Can't replace evap, don't exist. Took advice not to flush oil. Pump cannot be flushed anyhow. Remove pump drain plug, pour out old, measure, put back in same amount of ester/POE oil. Guessing I got 80% of oil out of pump. some mineral was is in evap/cond, don't care.
New drier ($35), Made my own new hoses cause motor swap, new pump brackets, and so on. New o-rings. Vac, fill to 80% of original unknown amount or 134.
Gauge reading are not what one would expect from web, as it is 134 in expansions valve system made for 12. hence don't over fill.
Cools well even when over 110*, and blow 32* out the vents.
 
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