Q: Is it possible for an air-conditioning compressor to go bad so quickly? Our daughter bought a 2007 Nissan Altima with 72,000 miles last August from a dealership, and now the AC doesn't work. She was told the compressor is dead. She'll get a second opinion, but I'm also wondering what your opinion might be.
Secondly, my husband drives a 2000 Jeep with 180,000 miles on it. A mechanic told him that to "save the life of his AC" he should use the recirculate button. He said the AC unit won't work as hard or cycle as much, and that'll keep him from having to deal with a problem like my daughter has. But I find it irritating because recirculated air gets stale and doesn't cool as efficiently in his car. I use the recirculate button only when we're following a stinky bus or truck. What's the real story?
A: The recirculate button, by closing off outside air intake to the system, allows the system to cool more quickly and efficiently, particularly in high temperature/high humidity conditions. I'm not sure this would be a significant factor in compressor life, but it certainly won't damage anything.
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The problem with your daughter's Nissan may not be the compressor itself. It may be the compressor clutch, engine management system or HVAC control module not signaling the compressor to engage. Most compressors that fail tend to make nasty noises when engaged, but low refrigerant pressure would prevent the system from allowing the compressor to engage.
Paul Brand, author of "How to Repair Your Car," is an automotive troubleshooter, driving instructor and former race-car driver. Email questions to him at paulbrand@startribune.com Please explain the problem in detail and include a daytime phone number.