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Soap bubbles and leak detection

There’s nothing cheaper or more benign than soap bubbles for finding a leak. As a technician with a 1999 Pontiac Bonneville complained, he tried trace dye and two different electronic leak detectors with no luck, despite the fact that the system was gushing between a half-pound and a pound overnight. But when he swabbed the compressor nose with soap solution, presto, it bubbled. His conclusion: back to basics does it.
We have to disagree.
Lab tests confirm that one bubble in 10 minutes might indicate a leak of 55 oz/year. That may not be the overnight gusher that the technician encountered, but it sure is a lot of refrigerant in an era of system charges of 12-24 oz on most cars, with even the large systems topping out at under 50 oz. So waiting 10 minutes or more to find even a relatively large refrigerant leak is hardly a practical approach.
In this case, the technician apparently became too focused on the evaporator when he didn’t find the leak underhood, even checking for dye in the condensate. Well, if the evaporator wasn’t leaking, it’s no surprise he didn’t find a dye trace that way. Also, even with an evaporator leak, the oil-bearing dye may be absorbed by debris on the evaporator core face or into a foam seal around the evaporator, and a dye trace might not show up in the condensate in any reasonable amount of time.
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.

If you’re a service professional and not a MACS member yet, you should be, click here for more information.

You can E-mail us at or visit to find a Mobile Air Conditioning Society member repair shop in your area. Visit to find out more about your car’s mobile A/C and engine cooling system.
The 32nd annual Mobile Air Conditioning Society (MACS) Worldwide Convention and Trade Show will take place January 18-20, 2012 at the Rio All Suite Hotel and Casino in Las Vegas, NV.

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