A conversion sticker should be placed on any system that has been converted from it's original refrigerant. At the very least, this is to make it easy for the next guy who may be a shop owner or other type of tech, that either wants to top up the system or to correctly reclaim the refrigerant. The sticker should include the type of refrigerant and type of lubricant in the system. The high and low side ports don't always tell the correct story. Don't make it difficult for the next guy. Also, contamination of reclaimed refrigerant is a big hassle (and expense) for the guy who is trying to do the right thing.

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95 E320 Cabriolet, 159K

Matt, with all due respect, you need to do some more reading on hydrocarbon refrigerants.

They're not like R12 or R134, where you need to have a completely dry environment for them to work properly. Hydrocarbons actually like a little moisture in the system. Not only does it do no harm, it actually increases the efficiency slightly.

Exactly.

But we're only talking about the 6oz-12oz (or less) of hydrocarbon refrigerant necessary to charge the average a/c system. Do you really think you're going to blow up the neighborhood with a couple ounces of propane? By that logic, I guess I'm endangering my life by having a butane cigarette lighter in my house?

Come on man...this is ridiculous.

Just vent some out. Duracool is environmentally friendly, you don't have to worry about venting it to the atmosphere.

Not only is a conversion sticker a good idea, IT'S FEDERAL LAW that a sticker along with unique fittings be put on any system to prevent the wrong refrigerant be added or from where I sit, an unidentified refrigerant be reclaimed.

If an unidentified refrigerant is reclaimed into a cylinder of legitimate refrigerant the ENTIRE cylinder is CONTAMINATED. Not only does the person reclaiming the junk lose the value of the legitimate refrigerant that was in the cylinder but he must PAY to dispose of it.

If you choose to use junk refrigerant, that's fine, but PLEASE at LEAST label it, so that some unsuspecting guy doesn't take a serious loss. Someone with a recycle/reclaim machine is just trying to put food on the table and shoes on the baby like everyone else. Give him a break!

I would not want any moisture in the system. As I have a car with PAG oil in it (was 134A) and now is also turned into Envirosafe (moisture + PAG = DEATH). Pull a vacuum regardless of refrigerant.

This is the procedure I follow:
1.- run the engine to normal operating temp
2.- put the car in high heat, close the windows (this will get the car HOT and toasty inside (evaporator warming). Or just let the car sit in the sun for a while before pulling the vacuum (try to reach at least 85-90 degrees inside the car)
3.- place a heat gun or hair drier at the receiver/drier (if not replaced, this will make it nice and hot, making sure the dissicant loses all the moisture during the vacuum)
4.- Pull a vacuum for 1 good hour (preferably when everything is hot, middle of the day, in the sun). Vacuum thru High AND Low side
5.- Close gauges valves and turn off pump
5.- Leave gauges on, make sure vacuum holds for at least one hour
6.- Pull another vacuum for 30 minutes

This will make sure ALL moisture Boils off from inside the system.

The question to which I have not found an answer is:

Does the moisture absorbed by the PAG oil boil off as well?

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

If the vacuum is low enough, the water should come out of the oil solution. The only question is how quickly does it come out... I don't know.

A fair point. My comment was directed to the original poster, who added grill quality propane atop R-12 and/or R-134a. So he now has water in combination with a chlorinated refrigerant. This is a recipe for an acid eat out.

How does water benefit a hydrocarbon only system? I would think the water vapor represents a dead load that causes work for the compressor but offers no cooling.

Not a chance. PAG doesn't merely absorb water. It polymerizes with it. No way are you getting it back out under any conditions that you are capable of making.

Besides the loss of lubricity when PAG and water mix, the mixture also flows very poorly at cold temperatures. This can inhibit the flow of oil through the evaporator.

Use the newer DEC-PAG instead. But if you're not flushing, you are stuck with what you have.

It is also worth noting that the SNAP rules only apply to ozone-depleting refrigerants, i.e., those that contain chlorine.

If your car was manufactured with 134a, the rules do NOT apply. You are free to convert it to hydrocarbons (modulo state and local laws) with only a labeling requirement. The fittings do not have to be changed.

Something tells me that in the not-too-distant future, we will be having this discussion again. Europe has already set the timetable to phase out 134a in favor of R744. I believe that it will be eventually banned here too. Then the question is staying with 134a (which will be the exact problem of staying with R12 today) or converting to HC. Or doing without.

If (when?) 134a is banned, do you suppose that they will update the SNAP rules, so that we are pretty much out of luck?

I'm not at all worried about the propane igniting when its contained in the A/C system - I'm worried about what happens when you are in an accident.

The A/C condenser is located in the front of the car and it is fairly weak, from my experiences in car collision repair most front end collisions that occur where impact speeds are more than 15-20 MPH will result in enough damage that whatever refrigerant is in the system WILL be vented to the atmosphere.

The vapor pressure of propane is around 100PSI at 85F, its not a matter of a couple of ounces in the condenser - all of the propane in the system will vaporize and escape at the rupture point. If you were lucky there would be a very large hole and the propane would escape very quickly, maybe 5-10 seconds for a large hole, if there wasn't an ignition source during that time period you would be fine. If there was a smaller hole you might have a bigger problem because it would take quite a bit longer for the propane to escape - your 20 minute estimate seems reasonable. Tell me would you be OK with an uncontrolled fire under your hood about the size of a campfire grill that went on for 15-20 minutes?

I'm certainly not saying that having propane in your system is a death sentence if it escapes but to say there isn't any risk is certainly not true.

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98 Dodge-Cummins pickup (123k)
13 GLK250 (135k)
06 E320CDI (323K)
16 C300 (62K)
82 300GD Gelaendewagen (54K)

I have had a high-pressure switch fail and an AC system (R12) rupture explosively in a mid-80's GM car at a stop light. It was momentarily as if a cloud surrounded the entire front of the car. Had this been propane, it might have been "even more exciting".

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

Hmmm...maybe I'm wrong here. Let's say the oil stays laying in the bottom of the compressor (although I think more would stay in the receiver/dryer).

Anyway, we have oil in the bottom of the compressor with no way to go anywhere. Would it likewise be safe to run our engine with no oil pump, just because the oil pan is full?

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2012 E350
2006 Callaway SC560

LOL
LOL


The pressure switch that cycles the clutch on and off is perfectly fine. A system charged with propane or duracool works at a lower pressure than R12 or R134. Therefore it never triggers the pressure switch which cycles the clutch on and off. On cars with electronic climate control that also utilize a temperature switch in the vents or cabin, its a different story.

Have you calibrated that thermometer? They come close, but never spot on.

You have a pressure switch in your low-side line? I think the older models may have had one, but our old '83 did not. The only pressure switch was in the high-side line.