R12 to 134a conversion or other options

[ISAslot]

It's hot. I've been thinking about converting over my Tercel's AC system. Currently it needs a charge, but the components appear to 'work' (just not very cold). If I do convert I'd like to do it the right way. Evacuate and flush the system, new oil and dryer, etc. However, I'm not sure what to do with the compressor. Seems you can't flush these, or convert the oil in them? Even If I could, I'd hate to do all the work and have it fail soon after. But I also wouldn't want to waste the current one by buying a new compressor. So, perhaps there's a way to make the system work without converting until it finally dies? Any suggestions?

I'm thinking we may try to salvage the R12 in my dad's old pickup and using that to make it functional for a bit.

 

[Bartman39]

If you go to all the trouble to do the conversion then just take the compressor off and rotate it by hand with the ports down to allow it to pump the oil out of it... Then just put the proper amount of oil for the retrofit back in it and reinstall... Flush the rest of the system and install the new dryer and evac the system and charge with 134a (proper way to do it)... Or the lazy way is to just evac the system to remove the R12 and charge it with 134a and in MOST cases it will last for some time (months to years)... But in most cases the condenser is about 30% to small for 134a to work perfectly but not always so it may work just fine...? Kinda a crap shoot but the key is how much 134a you put in the system... To much and will not work correctly and to little gives the same result just gotta find the balance... Its just so temp sensitive (134a that is)...

 

[Meghan54]

You can still find R-12 in the small cans for sale, but they do cost a buttload of $$. Thank goodness I've got some left courtesy of my brother who stocked up before R-12 disappeared.

 

[PottedMeat]

how long has it been 'not very cold' - sounds like it's got a minor leak. i'd get a can or two (~12oz each) of R12 off ebay or something and just top it off. they seem to be going for $~40.

conversion seems like a lot of work for a fairly old car

...damn i wish i bought those R12 cans i saw at a garage sale for $5/ea

 

[phucheneh]

'Conversion' is not a lot of work. Hell, you don't even need the fittings with a proper set of manifold gauges; with many, you simply unthread the r134 couplers off the end, and are left with the r12 ones. I'd recommend the fittings, though, since they're cheap.

Oil is circulated throughout the system. Yes, the compressor 'holds' oil, but it's generally in the same sense that other replaceable parts do. E.g. you'll add roughly as much oil for a condenser replacement as you will a compressor replacement in most cases. It is nigh-impossible to remove all the old oil, even with a long evac (suction held on the system). But you should try to get out as much as possible, as mineral oil will not circulate properly with r134.

You will add ester oil to the system (not PAG). Make sure the r134 you buy doesn't have oil in it. If it has dye in it, there is oil.

Drier is the only hard part that really should be replaced. Ignore people who tell you your old hoses are going to explode or some such garbage. R134 is more leak-prone, but there is no danger other than some lost refrigerant. I would just add some dye (put the concentrated stuff in with the ester oil) and charge it up, and see what happens. You'll know where any leaks are- will probably just be from old o-rings.

I would highly recommend buying or borrowing a real set of gauges, and not charging based on weight. Old compressors don't always cope with the 'proper' amount of refrigerant, and the system may perform better with slightly less. I charge based upon low side pressure- when the compressor is on the verge of being unable to pull the low side down to 30-35 pounds or so, you're done.

You've also got the conversion factor...even by weight, you would not charge to factory spec with r134. There's a percentage that most people use, but I don't remember it off the top of my head. Again, go by pressures and general system performance and you won't need to worry about it.

 

[Zenmervolt]

I would highly recommend buying or borrowing a real set of gauges, and not charging based on weight. Old compressors don't always cope with the 'proper' amount of refrigerant, and the system may perform better with slightly less. I charge based upon low side pressure- when the compressor is on the verge of being unable to pull the low side down to 30-35 pounds or so, you're done.

You've also got the conversion factor...even by weight, you would not charge to factory spec with r134. There's a percentage that most people use, but I don't remember it off the top of my head. Again, go by pressures and general system performance and you won't need to worry about it.

Definitely agree with this.

Though I've had good luck charging with the sight glass on older cars, pressures are better.

The only thing I'd add is that the low-side pressure will vary with ambient temps. On a 95-degree day low-side pressures with 135a might be only into the 40 PSI range but on a 60-degree day you might see low-side pressures down to 25 PSI.

ZV

 

[T2urtle]

There are r12 cans still around. Local guy had 12oz can and were asking $20 each. Sold all 6 instantly. He gets them time to time. Just see what's out there locally.

 

[thedarkwolf]

or you can just buy some freeze 12 or some of the other crap that is r12 compatible and just run that in the system as is. I did that on my old beater caravan for 12 years. Worked pretty well.

 

[Raizinman]

Don't forget Propane. I've converted numerous cars to Propane. Very cheap and very cold and very safe.

 

[Zenmervolt]

There are r12 cans still around. Local guy had 12oz can and were asking $20 each. Sold all 6 instantly. He gets them time to time. Just see what's out there locally.

Just remember that it's technically illegal to purchase R12 unless you have an EPA Section 609 Certification and illegal to sell R12 to anyone without that certification.

It's relatively cheap and easy to get (IIRC ~$20 and you can take the test online http://www.epatest.com/609/ ), but it's worth knowing that there's the potential for some heavy fines if you don't have it.

Don't forget Propane. I've converted numerous cars to Propane. Very cheap and very cold and very safe.

While I completely agree that it's safe (and VERY effective), I have to point out that using propane in an automobile HVAC unit is also illegal under EPA SNAP regulations if you're replacing R12. Several states also ban hydrocarbon-based refrigerants regardless of whether the system was originally R12 or not.

I'm not telling anyone what to do, just pointing out things they should be aware of.

ZV

 

[phucheneh]

I didn't think they were allowed to sell those maxoduraultracool refrigerants full of random flammable substances anymore. How exactly is it safe? I mean, under normal circumstances, sure; but under normal circumstances, Ford Pintos didn't explode, either.

A rock hole in a condenser plus an ignition source could equal an interesting 'event.' Hell, what if the condenser got puncture by a piece of metal that itself creates a spark, a la Pinto?

Just seems like a bad idea. Even if it wasn't flammable, propane is crazy sensitive to temperature. IIRC the pressure of propane in storage (in a can/tank) is something like 50psi around 32*F, and skyrockets to over 150psi at around 100*. R134 is sensitive, too, but not quite THAT sensitive. The 'alternative' refrigerants are something I've never had experience with, but when people ask, I generally just offer '...seems like a bad idea.' I wouldn't claim to be an expert...just would avoid them from a 'better safe than sorry' perspective.

Hell, I've barely ever even touched R12...I remember the first time I had to use a can, after using nothing but R134 machines...had never even used manifold gauges to charge. An older guy had to lend me a can tap, and show me how to stand there, shake the can, and watch the sight glass. One of those '...seriously?' kinda moments. 😀

 

[Zenmervolt]

I didn't think they were allowed to sell those maxoduraultracool refrigerants full of random flammable substances anymore. How exactly is it safe? I mean, under normal circumstances, sure; but under normal circumstances, Ford Pintos didn't explode, either.

They can sell them. Propane is probably the single most common industrial refrigerant in use today. It's used all over the place in industrial cooling units and has been since long before R12. As far as refrigerants go, Propane is superior to both R12 and R134a. It carries lubricant better, its temperature/pressure curves are better for refrigeration, and it's safer for the environment.

As for the Pinto, when you look at actual incidents of fires, the Pinto was less flammable than many other cars of the period (it placed roughly mid-pack). Even the infamous memo was simply Ford stating what numbers the NHTSA told automakers to use. But that's all a whole other topic. 🙂

The 'alternative' refrigerants are something I've never had experience with, but when people ask, I generally just offer '...seems like a bad idea.' I wouldn't claim to be an expert...just would avoid them from a 'better safe than sorry' perspective.

They're only "alternative" from a motor vehicle standpoint. Been safely in use in stationary systems for longer than I've been alive.

Hell, I've barely ever even touched R12...I remember the first time I had to use a can, after using nothing but R134 machines...had never even used manifold gauges to charge. An older guy had to lend me a can tap, and show me how to stand there, shake the can, and watch the sight glass. One of those '...seriously?' kinda moments. 😀

I can remember back when R12 came in big tanks like 134a does today. As a refrigerant, R12 was very good stuff. Better lubrication of the system, lower system pressures, better cooling (all compared to 134a, of course), just overall a better refrigerant. Except for that whole environment thing. 🙂

ZV

 

[thedarkwolf]

Nearly every fluid under the hood of your car is flammable. The small amount of stuff in your a/c is the one I would be least concerned about.

 

[steppinthrax]

Just remember that it's technically illegal to purchase R12 unless you have an EPA Section 609 Certification and illegal to sell R12 to anyone without that certification.

It's relatively cheap and easy to get (IIRC ~$20 and you can take the test online http://www.epatest.com/609/ ), but it's worth knowing that there's the potential for some heavy fines if you don't have it.



While I completely agree that it's safe (and VERY effective), I have to point out that using propane in an automobile HVAC unit is also illegal under EPA SNAP regulations if you're replacing R12. Several states also ban hydrocarbon-based refrigerants regardless of whether the system was originally R12 or not.

I'm not telling anyone what to do, just pointing out things they should be aware of.

ZV

How would this be safe, if he gets on leak in his system around a hot engine, or if he has a small amount of air circulating in his system while he puts in the propane.

They are selling, I believe it is R-427 or something like that as a drop in for older R-22 systems. Many people put this in to find that it's just straight propane!!!! Many HVAC tech caution against it.

 

[steppinthrax]

You're probably better off getting a shop to do it. You will need a few things that you probably don't have.

1. A vacuum pump.
2. Set of manifold gauges.
3. Flushing chemicals
4. Air compressor for circulating the flusher through
5. Nitrogen with regulator for drying out the insides of the lines.

In addition you probably would want to change out the seals, Schroeder valves, O-rings. You also need to evaluate the compressor to see if it's in good health. It might be worth wild to change the compressor as well.

 

[phucheneh]

Nearly every fluid under the hood of your car is flammable. The small amount of stuff in your a/c is the one I would be least concerned about.

Hold a cigarette lighter to a puddle of oil.

Now hold it up in a cloud of propane.

That's alls I'm sayin'. Refrigerant is not likely to meet an ignition source, but it would be the most flammable thing in your engine bay aside from gasoline. The latter's autoignition temperature is far lower, but it's also 1) a liquid, volatile vapors aside and 2) not held in a cooler in front of your radiator, nor is it inside the interior of your car.

Not to mention, autoignition temps don't tell the whole story. Throw a lit cigarette into a puddle of gasoline, and it will likely be smothered before it has a chance to cause ignition. Again...try the same with some gaseous propane. Or don't. Probably don't.

I don't think it's a high risk, but it's enough to discourage me from using it.

Also of note: R12 is not flammable, and while some of the R4xx refrigerant blends do contain propane, I believe it's a very low percentage. Like 5% or less.

 

[Zenmervolt]

How would this be safe, if he gets on leak in his system around a hot engine, or if he has a small amount of air circulating in his system while he puts in the propane.

The autoignition point is high enough that it would need to encounter an open flame to ignite. Simply having a small amount leak in a hot engine compartment would not be enough. Similarly, having some air in the A/C system would have absolutely no effect on anything. Propane doesn't spontaneously ignite when mixed with air.

I'm not saying he should do it. There are, after all, legal considerations that argue strongly against it. But it's not "unsafe" in the way that most people are worrying about.

They are selling, I believe it is R-427 or something like that as a drop in for older R-22 systems. Many people put this in to find that it's just straight propane!!!! Many HVAC tech caution against it.

HVAC techs caution against it because it's illegal. HVAC techs with experience in industrial cooling that I've spoken with have admitted that the illegality is the only reason to worry about using it in a car. The safety record in stationary systems is exemplary.

R-290/R-290a and R-600 are straight hydrocarbon refrigerants approved for stationary use and they're quite effective.

Again, I'm not saying to use them in cars. I have in the past (before I lived in a state which banned them) to replace R-134a and had no problems with them at that time, but I don't encourage others to do the same unless they are sure they are in compliance with EPA regulations and state law.

ZV

 

[dud]

OP, had the same issue with a older Lexus. My solution to the problem was to sell the car. I doubt that I will ever buy another car that uses R-12. It was a PITA ...