Propane for your A/C

[Raizinman]

Here we are with summer quickly approaching and people keeping their older cars longer and longer. Refrigerant leaking out and needing replacing. The price of R12 is very high and pretty difficult to even find. R134 can be had for 30 lbs for over $300 or individual cans for $20 each. This can get very expensive quickly. You can get a 40 lb container of propane at Lowes for about $80 (no license required). Even cheaper with coupons and sales.

Does anyone sell any type of valve to use your R12 or R134 gauges to put in propane? I suppose you could just cut the hose and use a barbed fitting with clamps.

I'm told the benefits of propane are:
1) Cheaper cost (especially if you have a slow leak)
2) Colder temperatures inside your car
3) Doesn't hurt the environment

I know lots of people use propane and haven't heard of any cars exploding due to propane. For that matter, if an A/C hose did come off quickly (which is rare), how would the propane ignite? You would need a source of ignition. It would likely disapate in the air quickly especially if the car is moving and the A/C fan is on, which it would be.

I would be interested in hearing results of others who have installed propane in R12 and R134 systems.

 

[cprince]

hmmm....interesting....I haven't heard of car exploding due to propane being used as a refrigerant, but I haven't heard of any car that use propane either. There are many sources of ignition in the car--especially old cars: switches(ignition switch, turn signal, wiper, fan, power windows, power lock), hot engine, moving parts in the hood that might make a spark. Here's one scenario: Your car has a small leak in the evaporator and you park it night. Propane slowly fill the passenger compartment, and in the morning you insert the key to open the door and the power lock switch causes a spark. The whole car blows up in your face!

 

[Lotheron]

This has already been discussed:

http://forums.anandtech.com/showthread.php?t=164250

I wouldn't do it though...

 

[IcePickFreak]

The vapor pressure between R134 or R12 and propane are quite a bit off, then you'd also have to consider latent heat, how much do you put in etc.

Refrigerant Vapor Pressure
Propane Vapor Pressure

Besides all that, I think using it in this application is plain crazy at face value. Consider that even an improper propane/oxygen for ignition can create carbon monoxide - ie. you get a leak in the heat exchanger in your recirculation system and end up pumping CO into your interior where you have all the windows up.

 

[Eli]

People have been doing this for years and years.

 

[hdfxst]

If propane wasn't flammable it would be the perfect refrigerant.It works with any oil and is almost a direct replacement for R22

 

[cprince]

People have been doing this for years and years.

either provide sources or tell me that my sarcastic detector is not working today

 

[Eli]

either provide sources or tell me that my sarcastic detector is not working today

I heard about using propane as a replacement for normal refrigerants 15 years ago. I'm sure there were plenty of people doing it before that.

 

[slag]

No, he's right, they have been doing it forever. Doesn't mean its a good idea though.

 

[IcePickFreak]

Yup I've heard of people doing it for a long time as well, course it was always a friends uncles buddy, etc. I've also heard of people strangling themselves while beating off. (RIP David Carradine)

 

[JeffreyLebowski]

Depending on where you live, just drive down to mexico and get r12. Dirt cheap.

 

[radioouman]

I just bought cans of R134a for $14 each. (16 oz cans I believe) Since my car takes 2.5 lbs, the refrigerant really wasn't that much of a cost.

(My AC system didn't have a slow leak, the compressor failed. I had to replace the compressor, thermal expansion valve and dryer, then vacuum it, charge it up and check for leaks. As I said above, when you look at the other costs, the refrigerant didn't cost much at all.)

 

[drnickriviera]

R-12 is not hard to find. Napa will usually keep a few cans in stock. $40+ a can though. I just bought a 14oz can off ebay for $24. Keep an eye on craigslist. People will usually sell 30lb cylinders

 

[brblx]

r134a is too expensive? that's a joke, right?

convert to r134a. do not run propane or any other of the name-brand gas 'blends.' if a couple pounds of 134 hurts your wallet that bad, quit driving.

a conversion basically consists of threading new fittings onto the old R12 ones and refilling the system. ideally the leftover r12 oil needs to come out, though. i believe ester oil will mix with it (PAG won't), but it's still a good idea to change the dryer and evac the system (i'd suck it down for at least 20-30 mins, more won't hurt).