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Can an aluminum a/c line from a car be tig welded?It has a small crack no gap about 1/8 inch long running around the dia. of the tubing which is about 3./8 in. Should I be concerned about any dangerous gasses from the freon etc. Thanks
Reply:If you have actual FREON, R12,  then yes, heating it makes  nerve gas... very dangerous. if you have R134a perhaps not....but the main thing is that that is not a legit fix on several levels.... first it is not likely to work unless you fix whatever caused it... check to see if your AC compressor and other things are mounted like they are supposed to be..  Also, if you did weld on it you would want to have nitrogen or argon inside it as a purge... as later on the stuff which comes off that burned area inside the line will likely mess up your AC system.... clogging the small places like the TXvalve or the fixed orifice depending on the type system you have...   And , you need to evacuate the system anyway... as any moisture in there will mix with the oil and cause an acid to form ...which will eat away at the insides of the metal lines in the system... causing the same type of problem as an unprotected (non purged with inert gas ) weld area will.   So, since you need to evacuate, probably flush, renew the Receiver Drier anyway.. due to the compromised opening suggested by the crack..... it makes much more sense to replace that line if available.... or at the very least do the fix off the car.Weldandpower Lincoln 225 AC,DC with Briggs 16hp gas engine.WW2 era Miller TIG.
Reply:I think you should be more concerned about causing any contamination on the inside of the line.  Best to remove it from the car if you can and attach to a nitrogen source, then pass a low volume of nitrogen thru the line while you are welding.    If you can't remove it, just unscrew it from each end and hook the N source to one end.  Nitrogen is inert and will not support combustion and will prevent all the crud from forming inside the line.  Now, I know the above to be true for silver soldering on AC lines, I can't say for certain if your are Tigging an alum. line, but I presume the same principles will hold true.JamesArtist Blacksmith
Reply:I flush ac lines with mineral spirits, use compressed air to dry. Wire brush area and tig with 4043. Blow out line, close one end and pressurize with air from other end, check with soapy water for leaks. I do a bunch starting each spring and these stop comming in in the winter. I get these from several local shops and also the Chevy and Ford dealers in town.  Simple easy money maker. Never had one fail. PeterEquipment:2  old paws2  eyes (that don't look so good)1  bad back
Reply:Originally Posted by GBMIf you have actual FREON, R12,  then yes, heating it makes  nerve gas... very dangerous.
Reply:Originally Posted by castweldI flush ac lines with mineral spirits, use compressed air to dry. Wire brush area and tig with 4043. Blow out line, close one end and pressurize with air from other end, check with soapy water for leaks. I do a bunch starting each spring and these stop comming in in the winter. I get these from several local shops and also the Chevy and Ford dealers in town.  Simple easy money maker. Never had one fail. Peter