Clean the aluminum AC line with a steel wool pad. Scrub until the bare aluminum shows through and no dirt or grime remain on the line.
Light a propane or acetylene torch. Allow it to heat up for five to seven seconds and hold it 4 to 6 inches away from the aluminum AC line. Heat the aluminum line by waving the flame up and down, back and forth.
Melt aluminum flux weld onto the AC line where the aluminum is cracked or a hole has appeared. Allow the aluminum flux weld to drip onto the broken part of the aluminum line. It will quickly repair the compromised part of the AC line and patch it with a like color.
Let the aluminum flux weld cool for about five to 10 minutes, then rub with a microfiber cloth to polish the patch.