what are the weak links in an auto AC system? - Page 2 - PeachParts Mercedes-Benz Forum

johnjzjz · #16 01-28-2010, 03:41 PM

the old shop has 2 complete systems and we dont mix it yes the oil we buy is different as well, as the O Ring box is different type or rubber seals you can feel the difference and of course the oring colors are different 12 and 134

but some people have a way to do things we just wont do - jz

Chas H · #17 01-28-2010, 03:49 PM

Quote:

Originally Posted by gmercoleza

No need to waste precious R12. Just put a $8 can of R134A with UV dye into the system yourself. Turn the A/C on for about 1 minute to circulate, then shut it off and go searching with your black light. The R134A eventually evaporates out of the system, and there's no harm done.

This is not a good idea. As John mentioned the shop can fill the system with R12 then remove the remaining R-12 after the leak is found.
It is illegal to mix R-12 and other refrigerants and poses a risk of contaminating the supply of refrigerant at a shop.
Dye works well for underhood leaks. The air moving around when the engine is running makes the use of a sniffer iffy.

gmercoleza · #18 01-28-2010, 04:06 PM

Quote:

Originally Posted by Chas H

This is not a good idea. As John mentioned the shop can fill the system with R12 then remove the remaining R-12 after the leak is found.
It is illegal to mix R-12 and other refrigerants and poses a risk of contaminating the supply of refrigerant at a shop.
Dye works well for underhood leaks. The air moving around when the engine is running makes the use of a sniffer iffy.

You are correct - mixing R12 with other refrigerants is both illegal and unethical. However, you are not mixing with R12 if there is no R12 currently in the system (it all leaked out). After the leak is repaired, there won't be any R134A in the system either, so you can just charge back up with R12 and go.

johnjzjz · #19 01-28-2010, 04:08 PM

so the oil wont be contaminated i will try and remember that - jz

gmercoleza · #20 01-28-2010, 04:14 PM

R134A mixes poorly with mineral oil. In addition, it is highly volatile and will completely boil away after 30 minutes of deep vacuum.

johnjzjz · #21 01-28-2010, 04:16 PM

got a link on that ???? idea - jz

gmercoleza · #22 01-28-2010, 04:17 PM

Quote:

Originally Posted by johnjzjz

got a link on that ???? idea - jz

Nope, no link. Got one for yours?

gmercoleza · #23 01-28-2010, 04:30 PM

Actually, here's a link. Boiling point of DuPont SUVA is minus 26.5 degrees celsius. So you wouldn't even need to pull a vacuum to get it all boiled out. Just opening the system to repair the leak will result in all R134A being removed from the system: Info From DuPont's Website.

Since the R134A will not mix with the existing mineral oil (which is not hygroscopic like PAG or Ester, by the way), logic dictates that it will boil out.

gmercoleza · #24 01-28-2010, 04:34 PM

When a system is converted from R12 to R134A, part of the proper procedure is flushing all the old mineral oil out and replacing with either PAG or Ester. Why is that? Because mineral oil will not mix with the R134A, therefore it will not get carried throughout the system for proper lubrication.

Similarly, oil and water (which is far less volatile than R134A) do not mix. If you boil an oil/water mixture in a pot on the stove, I assure you after some time there won't be any water left in that pot.

Separate gauges and hoses are used for R134A and R12 systems mainly to prevent cross-contamination of the oils, which are completely incompatible.

Chas H · #25 01-28-2010, 04:36 PM

Quote:

Originally Posted by gmercoleza

You are correct - mixing R12 with other refrigerants is both illegal and unethical. However, you are not mixing with R12 if there is no R12 currently in the system (it all leaked out). After the leak is repaired, there won't be any R134A in the system either, so you can just charge back up with R12 and go.

The refrigerant -either R-12 or 134 will leak out until the system pressure equals ambient pressure. All the refrigerant will not leak out.

gmercoleza · #26 01-28-2010, 04:44 PM

Quote:

Originally Posted by Chas H

The refrigerant -either R-12 or 134 will leak out until the system pressure equals ambient pressure. All the refrigerant will not leak out.

Fine, then just pull a vacuum for a couple minutes. Problem solved.

Either way, the point is that you CAN use R134a to test for leaks in an R12 system without any ill effects. A/C shops commonly use a few oz. of R134a pressurized with nitrogen to test for leaks.

TimFreeh · #27 01-28-2010, 05:17 PM

Quote:

Originally Posted by gmercoleza

Either way, the point is that you CAN use R134a to test for leaks in an R12 system without any ill effects. A/C shops commonly use a few oz. of R134a pressurized with nitrogen to test for leaks.

The only ill effect would be that you are violating the EPA rules that govern the venting of refrigerants.

http://www.epa.gov/Ozone/title6/608/608fact.html#noventing

gmercoleza · #28 01-28-2010, 05:19 PM

Quote:

Originally Posted by TimFreeh

The only ill effect would be that you are violating the EPA rules that govern the venting of refrigerants.

http://www.epa.gov/Ozone/title6/608/608fact.html#noventing

Who said anything about venting? I don't recall seeing that word anywhere. Pull a vacuum with a recovery machine and retrieve the refrigerant rather than venting it.

I used the words "ill effect" in reference to the supposed harm that others say would be caused to an R12 system by using R134a to test for leaks. There are two distinct issues here at play which you are attempting to blend into one:

1) is it legal?
2) is it harmful to the system?

TimFreeh · #29 01-28-2010, 05:28 PM

Quote:

Originally Posted by gmercoleza

Who said anything about venting? I don't recall seeing that word anywhere. Pull a vacuum with a recovery machine and retrieve the refrigerant rather than venting it.

I used the words "ill effect" in reference to the supposed harm that others say would be caused to an R12 system by using R134a to test for leaks. There are two distinct issues here at play which you are attempting to blend into one:

1) is it legal?
2) is it harmful to the system?

I'm not offering an opinion about using R134 in an R12 system, I wouldn't do it but that's just because I have access to refrigerant recovery machines. I suspect it would work fine.

One of your prior posts suggested that the R134a would be gone after you opened the system to repair the leak, I'm assuming it would be "gone" as in 'evaporated to the atmosphere' gone. If you meant it would be recycled I'm guessing that would be fine and dandy.

In reviewing the specific lists of CFC's and HCFC's in the fed regulations I don't see R134a mentioned as a refrigerant governed by the 'no vent' requirement - so you may be OK even if you vented it to the atmosphere.

When I got my 608 certification I was under the impression that venting R134a was illegal, I'll have to review my notes and see if my memory was correct.

gmercoleza · #30 01-28-2010, 05:32 PM

Yes, when I got my 608 I recall reading some language somewhere which implied that venting R134A was also illegal. The language was vague and probably open to interpretation, but that's how I read it.

As for "using R134A in an R12 system" I'm not saying to do this permanently. Just use a small amount with UV dye to enable the system to cycle on for a minute or two and distribute the dye.

And yes, whether legal or not, I'm sure there are plenty of people out there who open the system to repair a leak WITHOUT recovering, thus my assumption that the refrigerant would leak out completely anyway.