One good gauge set, two refrigerants

[JHZR2]

None of my cars have recurring AC charging needs, but I bought a good us made set of gauges and 30# of r134 back when it was cheap.

I use it now and again to see if I need to top up a car or help friends.

Two of my cars run r12. They are 30yo and I'm not converting an old system like that. One after many years of good service is showing bubbles in the sightglass. I need to add r12.

I'm considering taking the test and being able to have my own r12. I don't do enough work, nor do I plan to, to justify a set of r12 gauges.

So is there an acceptable way to use one set of gauges for two refrigerants without causing issues?

Thanks!

 

[Keith_Stone]

Sure, it's done all the time. Locate a pressure/temperature chart(google)and use the psig markings on the manifold gauges. You can cross contaminate oils up to 5% of compressor sump volumes before problems occur. Switching between R12(mineral oil) and R134a(POE) with the same manifold would take many many times to create any oil contamination issues. We do it all the time in the hvac industry with R22 & R410a.
However R12 and R134a use different fittings. You'll need adapters on your suction/discharge hose ends if you still have the OEM R12 fittings on your vehicle.

 

[Bluestream]

As far as I know R12 is a restricted product. I know we could get fined or go to jail for using it here...

 

[Keith_Stone]

No Federal restriction on using CFC refrigs. here in the usa.

 

[JHZR2]

Originally Posted By: Bluestream
As far as I know R12 is a restricted product. I know we could get fined or go to jail for using it here...


Not particularly... Just need to take an (open book) test and you can legally purchase.

Since any evacuation and major work would be done by a shop, all I'm really concerned with is buying it for my older cars...

 

[JHZR2]

Originally Posted By: Keith_Stone
Sure, it's done all the time. Locate a pressure/temperature chart(google)and use the psig markings on the manifold gauges. You can cross contaminate oils up to 5% of compressor sump volumes before problems occur. Switching between R12(mineral oil) and R134a(POE) with the same manifold would take many many times to create any oil contamination issues. We do it all the time in the hvac industry with R22 & R410a.
However R12 and R134a use different fittings. You'll need adapters on your suction/discharge hose ends if you still have the OEM R12 fittings on your vehicle.


If all I'm doing is recharging, is oil contamination an issue? Or do you mean the other refrigerant contaminating the oil in the system?

 

[exranger06]

There are many gauge sets you can buy that can be used for both R12 and R134a, so I don't think using the same gauges would cause any problems. You would need adaptors for the hoses. The gauge set I bought is advertised as an R134a only set, but it has two different scales on the gauges, one of them is for R12. So your gauges probably wouldn't be accurate using R12.

 

[Keith_Stone]

Hoses will pickup small amounts of oil when put on any system. Going between mineral oil based systems and POE/PAG based systems COULD possibly contaminate if done repeatedly. But, I've never seen it in the real world. I often blow out the hoses with dry nitrogen if I feel ever it's an issue.

 

[JHZR2]

Originally Posted By: Keith_Stone
Hoses will pickup small amounts of oil when put on any system. Going between mineral oil based systems and POE/PAG based systems COULD possibly contaminate if done repeatedly. But, I've never seen it in the real world. I often blow out the hoses with dry nitrogen if I feel ever it's an issue.
.

I generally keep mine with a slight overpressure of refrigerant to prevent moisture entry.

Would it be better for me to purge with dry N2 as a matter of course?

 

[Keith_Stone]

I think the big issue in a small refrigeration system such as automotive ac is keeping non-condensables(air)out of the system. I like to purge the hoses with a small amount of freon I'm using on the system. Screw on the hose ends loosly on the fittings(a turn or two)Open valves on manifold slightly to purge air from the hoses. I look for a slight "spit" of freon, then close the manifold valves and tighten the hose ends on your system. Then procede. It works good on R134a manifolds with collet adapters on 1/4" flare hose ends.
I'm using the term "freon" as a general reference.

 

[Keith_Stone]

Originally Posted By: JHZR2
Originally Posted By: Keith_Stone
Hoses will pickup small amounts of oil when put on any system. Going between mineral oil based systems and POE/PAG based systems COULD possibly contaminate if done repeatedly. But, I've never seen it in the real world. I often blow out the hoses with dry nitrogen if I feel ever it's an issue.
.

I generally keep mine with a slight overpressure of refrigerant to prevent moisture entry.

Would it be better for me to purge with dry N2 as a matter of course?
If you have access to nitrogen it certainly won't hurt. Then purge with the refrigerant required. Miniscule amounts of refrigerant loss when attaching/detaching hoses is permitted under epa guidelines.

 

[AstroTurf]

Where will you purchase R12 from?

Thanks, Jim

 

[bullwinkle]

The supply houses should be able to get it for you if you have an EPA license to buy it with, I've even heard that the price on R-12 actually came down to $800/30 pound can, it was upwards of $1200 for a while.