Aluminium pipe repair - car air con

[alan_man]

Hi guys, firstly apologies if this is in the wrong section, mods feel free to move this to the suitable section. My car's air conditioning system is running R134a utilising aluminum pipework throughout the system for both high and low sides. The previous owner had the system repaired/recharged some years ago with the addition of dye for leak detection. I was poking my head around the motor the other day when I noticed some green dye around the weld for the high side service valve. I cleaned the dye off and observed the area for a couple of minutes. I've found there is the smallest of leaks through the weld on the pipe, you can barely just see the formation of dye coming out the leak. Once enough dye has accumulated around the hole you can see small bubbles forming as well. I was wondering if you are able to perform some minor brazing with aluminium without having to recover/recharge the refrigerant in the system? The air con still works great, I believe this has only occurred in the last week or so and I there is still most of the refrigerant remaining in the system. Excuse the lack of knowlege as I only deal with domestic split systems and copper piping. Thanks in advance

[JoeAT50A]

Handling of gas leak and system related issue are nothing to do with Copper or Aluminium tubes I believed.
Sometime you might seen flexible pipes. Leak is Leak, best is to follow good practices like pumpdown, vaccuming, leak test and recharge. Some coutries are start using Aluminium tube now due to copper price hike.
Have you ever done those small/micron leaks with copper tube? Please apply the same.

[Latte]

. I was wondering if you are able to perform some minor brazing with aluminium without having to recover/recharge the refrigerant in the system?

Not unless you want to knock youreself out with mustard gas (Thats what occures, or a least very close to) if you do any braising with gas in. Gas MUST come out first, repair done, leak test with OFN, drier change, vac and regas. This is not a DIY repair im afraid, get a specalist in

[charlie patt]

you cannot weld it with gas in degas it change the pipe or tig it or fit a vulcan lockring just be carefull it is actually leaking when the uv went in he may of put it in the high side and it could be just sitting in the welded area if it is leaking on the high side due to pressure the refrigerant charge would be low within a month

[Karl Hofmann]

The alloy is brazeable but practice on scraps of pipe first....a lot!..... But when you try to do your car, remove the refrigerant first. Failure to remove the R134a will make your attempts very YouTubeable.

[alan_man]

Thanks to all for the helpful replies, looks like I will go about repairing just like any other system. Shame but that's life, I doubted an easy fix in the first place but hey no harm in asking questions. Thanks again

[r.bartlett]

Not unless you want to knock youreself out with mustard gas (Thats what occures, or a least very close to) if you do any braising with gas in. Gas MUST come out first, repair done, leak test with OFN, drier change, vac and regas. This is not a DIY repair im afraid, get a specalist in

Mustard gas -how's that work with 134a?

[stufus]

Read this an another forum , thought it was a good explanation to the misconception.

Mustard gas is actually a liquid that can be created by reacting ethylene with sulfur monochloride or S2Cl2.

"Mustard gas causes severe blistering even in small quantities. It is highly irritating to any sensitive areas, especially the eyes.In many cases it causes blindness. If inhaled, it attacks the respiratory tract and lungs, causing pulmonary edema. Some effects of exposure to mustard gas are delayed up to 12 hours and death may result several days after exposure. "(2)

Chemically, mustard gas is a thioether, 2, dichlorodiethyl sulfide, (ClCH 2 CH 2 ) 2 S. It can be prepared by reacting ethylene with sulfur monochloride, S 2 Cl 2 , or by other methods. Its vesicant property is readily destroyed either by oxidation or by chlorination (e.g., with bleaching powder). (1)

Mustard gas is similar to phosgene, which is a colorless poison gas, first used during World War I by the Germans (1915). "(3)

Phosgene is a major industrial chemical used to make plastics and pesticides and is a poisonous gas. It has been used as a choking or (pulmonary) agent. Phosgene is also known by its military designation, “CG.” Phosgene can be formed when certain compounds are exposed to heat or burned. (4)

Propane = 'Formula: C3H8' and it one of the lightest, simplest hydrocarbons. (5) It also has a Chemical identifier in the HVAC industry as HC-290. HFC-134a is a hydroflorocarbon. The burning or chlorine, florides, hydrocarbons (HC), or hydroflorocarbons (HFC) can cause poision gas similar to phosgene or mustard gas with similar effects on the body.

here is the first of a 3 part discussion we had about green gas being propane

read this for more interesting facts about Chemical Warfare Agents



1. http://www.encyclopedia.com/html/m1/mustardg.asp
2. http://web1.caryacademy.org/chemistr...ing%20page.htm
3. http://www.encyclopedia.com/searchpo...arget=phosgene
4. http://www.bt.cdc.gov/agent/phosgene/basics/facts.asp
5. http://www.weldingsupply.net/propane.htm

Cheers
Stu

[Karl Hofmann]

Crikey... Burning hydrocarbons produces Mustard gas???? Thank god I have an electrc hob!.... Still it gives me a perfect excuse to ID gas fires.

[charlie patt]

karl what are you braizing the alloy with every time i have tried it on a car the alloy is that thin it just blows it away

[Brian_UK]

How to weld aluminium..

http://www.amweld.com.au/welding-aluminium.htm

Also, aluminium repair kit...
http://www.durafix.com.au/index.php

[Airconjohan]

I would agree that the refrigerant need to be recovered first. The best alternative would be a Vulkan Lokring High side fitting as long as the size of the existing pipe is compatible with the size of the fitting. They will squash down to fit a pipe perhaps 20 thou (sorry Oz, half a mm) smaller but is is obviously better to have an exact fit. Needs a good inch of straight pipe each way for a good fit. Once done will never give trouble.