Written by Topher Kessler
The wireless connection on Macs is set up by default through the Airport card, though third-party solutions are supported as well. Regardless of the method used, there may be instances where the computer will report no card present, even though one is installed and was working just fine.
Apple discussion poster "Alex222" writes:
"Two weeks ago I went to turn on my airport by using the menu bar, and the only thing the drop down menu told me was 'No airport card installed'. What happened to it? It was working fine before. How do I get my card working again?"
As a first step, try resetting the computer's PRAM and SMC, because an improper setting may prevent the card from being loaded in hardware and prevent the system from recognizing it. Being the least-invasive step to take, this is the first recommendation to fixing this problem. Resetting the PRAM and SMC will not harm your computer, though you may need to set some system settings again, such as the default resolution, sound volume, and mouse speed.
Sometimes cards cannot be loaded properly if there is a driver or system software conflict that interferes with it; however, the card should still be detected in hardware and appear as an available device. To see if the card is being detected, open System Profiler and check for the airport card under the "Network" section. Additionally, you can try booting off the OS X installation DVD that should provide Wi-Fi support. If the card is working properly, booting off the DVD should allow it to be activated (go to the AirPort menu and enable the card there) and help you determine if the problem is with the card or with your system software installation.
Apple's AirPort modules for wireless connectivity are separate cards that either plug directly into the motherboard or are connected by wires or ribbons. While they are usually secured to the computer chassis, sometimes and especially on portable computers they or their connections may be jarred loose. If this is the case, the card may not load at boot and you will not have wireless connectivity.
For Mac Pro and older PowerMac systems, the card can be easily accessible through the service door, so you can try reseating it or checking the connections; however, for portable systems the card is harder to access so we recommend you take the computer in to an Apple store for servicing. If you are up to the challenge, there is a variety of take-apart guides online that you can use to try to service the computer yourself. The following are just a couple of resources where you can find video and picture guides for servicing your Mac (among other devices):
Topher has been an avid Mac user for the past 10-15 years, and has been a contributing author to MacFixIt for just over a year now. One of his diehard passions has been troubleshooting Mac problems and making the best use of Macs and Apple hardware both for family and friends, as well as in the workplace. He and the newly formed MacFixIt team are hoping to bring enhanced and more personable content to our readers, and keep the MacFixIt community going here at CNET. If you have questions or comments for Topher or the other MacFixIt editors, feel free to contact us at http://www.macfixit.com/contactResources