Should convert to R134a on my BJ74 or just find some R12 or R12a? (1 Viewer)

[Bob Richards]

My AC does cool some and last summer it was freezing cold. I think I just need a boost but reading into it I guess to convert I have to recover what R12 is remaining and perform a series of activities so I can charge it w/134a... What is everyone else doi?

 

[jakerudy]

Legally you are supposed to recover the R-12. How often does that happen is anyone's guess. Without a recovery machine it is almost impossible so if you have access to one or a shop that will do it great. Otherwise you can use a cylinder in a bucket of ice water and recover all you can from the system.

Evidently you can find some R-12 on the internet but need to be careful with the seller. 12 is expensive and there is some counterfeit stuff out there but that would be the easiest fix.

In theory the swap to R-134a requires new o-rings, a system flush of the mineral oil, and a charge with PAG lubricant. In reality with such a small system you can evacuate it and charge with R-134a and it will be fine. 134a isn't as efficient as 12 so the cooling capacity will be reduced a little. If you have a leak now it will probably be a little worse with 134a so either go through the entire system or expect to top it off occasionally.

 

[jblueridge]

After looking into buying specialized tools and materials, I stumbled across a shop that insisted on using R12.
The freon was expensive but I think balanced well against o-rings, system flush, etc.

 

[RhinoRig]

Digging into that now with an HVAC buddy that knows his shiznit. I'll post news

 

[Bob Richards]

I figured with summer here several of use would at least be thinking about this. Really appreciate all your insight.

 

[NGray]

I had mine converted. Oiled, new fittings and freon for around $100. It was a while ago, so I forget the exact cost. I've have a slow leak somewhere in my system and figured converting it would be easier for me so I can top the freon off every other year.

 

[FullyLitLED]

Does anyone have an average cost of doing this? I found a shop in my area but do not know if they are a rip or not...

 

[Bob Richards]

I called 4 different places ranging from recommending a full replacement of the system to just adding to it... the cheapest swap with replacing the seals was $125 then $250 and up.

 

[FullyLitLED]

Ok I got a quote for $225 so I guess it is a decent price point

 

[jblueridge]

I was told that these older systems use a lot more refrigerant than newer ones.
I think $225 sounds good if they are going to replace orings and stuff.

 

[jakerudy]

I was told that these older systems use a lot more refrigerant than newer ones.
I think $225 sounds good if they are going to replace orings and stuff.

Be wary of that advice. Auto a/c units usually use around 1.5 - 2 lbs of refrigerant. Refrigerants have changed over time but thermodynamics have not.

R-12 is expensive since it was banned years ago but you can get R-134a at Wal-Mart so it isn't rare. The shops buy it in jugs so pay a fraction of the cost per lb that you can get retail. Most of the cost of the conversion is labor as o-rings are cheap. Pretty much every auto a/c system leaks due to o-rings and vibration. It is just a matter of how fast it leaks.

$225 is probably not unreasonable given the time to replace the o-rings, pulling a vacuum, and overhead to have the stuff to do it. R-134a and lubricant are not the major cost.

 

[jblueridge]

I found this image on a site about the new 1234yf refrigerant. (See link below)
My BJ74 uses more than 1.1 pounds of refrigerant.

Laws of Thermodynamics don't change but advances in materials and manufacturing mean more efficient condensors, evaporators and perhaps compressors too.

This link also mentions Mercedes Benz CO2 refrigerant aircon system.

HVAC: A/C Update For R1234yf Refrigerants

 

[jakerudy]

I have no experience with R1234yf.

There are many options for refrigerants that have been shot down for various reasons. Propane is a near drop in for R-22 but flammability ruled that out for home a/c. CO2 is an efficient refrigerant but the operating pressure requires a complete system redesign - not a conversion. The blends have a temperature glide at the evaporator.

Advances in technology might result in more efficient systems but I suspect you would have to replace the entire system on an older vehicle for any significant improvement.

 

[jblueridge]

I am not an expert, I just read stuff.
Refrigerant 1234yf can be put into R134a systems. The R134a has to be removed and purged I guess.
1234yf decomposes quickly when it is released into the air: fewer climate change effcts.

Newer ideas include a double loop system similar to "chiller" ac used in large buildngs.
A safe liquid like water with anti-rust chemicals circulates to a heat exchanger n the engine bay. This water is cooled by the compreessor and refrigerant. The amount of pipng for the "freon" would be much less: lower probability of leaks. A pump is needed to move the cold water around.

As you say, not much use for a cruiser without a total re-design.

 

[thzpcs]

You can still find shops that are certified for R-12, but it'll be a huge pain in the butt if you plan on keeping it much longer. For the $150, it's a lot better to just convert it to R134, it'll save a lot of headache down the road.

 

[FJ73Texas]

I just had my system converted over to R134 after getting the clutch pulley repaired. It doesn't seem to blow as cold as it did when it had R12. Still pretty cold though!

 

[Bob Richards]

What did they charge you?

 

[FJ73Texas]

There was other labor involved such as repairing the clutch pulley and installing new OEM Denso compressor. I would guess the conversion itself was probably $200 labor.

 

[WanderinWhitlows]

R12 is banned for automotive use as mentioned earlier. It isn't banned for agricultural use and can be found at commercial tractor stores. My local John Deere farm equipment store carries it as their large tractors and harvesters have air conditioned cabs.

 

[jakerudy]

R12 is banned for automotive use as mentioned earlier. It isn't banned for agricultural use and can be found at commercial tractor stores. My local John Deere farm equipment store carries it as their large tractors and harvesters have air conditioned cabs.

Interesting info. I haven't seen it at my local dealers. Can you get it for your own use or is it reserved for the dealer?