Will replacing wi-fi card fix iMac wi-fi connectivity issues?

It's under warranty, take it back. If you do it soon enough, and it's defective, they may just replace the whole thing.

Since you appear to be stealing access from other peoples wifi networks, you might try moving your iMac's location to try for a better connection.

1.5hrs is probably a lot less time than you're going to spend on this problem if it is faulty hardware. Take it back, have them verify that it works or replace the hardware.

If it still doesn't work when you get it back home, chances are you need a new router. Get a dual-band one to reduce interference from all those signals around you.

He doesn't have a router. He's using his neighbors unprotected wifi connections.

From OP:

Tonight I've been able to get it to limp along by leaving the computer on for a while, connecting to an unprotected network, and running a constant ping to google.com through network utility......

I can get ethernet but I'd rather not pay for it when there are two or three perfectly good wi-fi connections in my building.

Thanks Lanny, I spotted that on the re-read.

Well, chances are the problem is that those wifi connections are a bit more flakey than the OP suggests, but since the machine is still under warrantly, its pointless doing anything else than getting the hardware checked out first, as you said yourself.

Sorry but GET A LIFE and STOP STEALING FROM OTHER PEOPLE.

LO8A wrote:

You probably shouldn't assume that someone is "stealing" their neighbor's Internet.

No, I never suggested that at all. Also, if you're so sure about the answer to the problem, why bother coming on here and wasting our time asking for our advice??

Good luck solving your problem on your own. 😎

A lot of folks have had this wifi problem which started or accelerated with Lion upgrades. I have yet to hear of a hardware fix taking care of this and, other than constant pings, I haven't run into a software fix that works yet, either. Apple products are usually quite good, but when they have a fundamental problem like this they have a poor track record on addressing it, so don't hold your breath. The last Lion update which was supposed to include a wifi fix made my wireless connection worse.

I apologize for the other people on this forum. For some reason such finger wagging is popular on Apple forums, especially by rude people who don't know what they're talking about. I wish you the best of luck.

LO8A wrote:

I think you're right based on what I've read elsewhere. I sort of figured as much, which is why I did not end up going in for authorized repair.

And you (and your friend, there, who I'm glad to see edited his first unnecessarily abusive posting) are missing the point of the advice given.

You are making an ASSUMPTION that your problem is the same as other people who've posted about wifi problems. The difference, in your case, you've got brand new hardware which worked for 3 days and now has stopped working. Even an Apple technician told you to check out the hardware.

What makes you so sure there is not a hardware fault in YOUR case (regardless of what the fault is in other people's case). Do you think hardware faults are unknown? Since you have a warranty, do you think it is not WISE to have the hardware checked so that you can RULE THAT OUT as a possibility?

I really fail to understand why you don't take the common sense next step and have the h/w checked out. If that doesn't solve it, you haven't wasted 1.5hr — you'vel narrowed down the possible causes.

At the moment, you have NO IDEA of the cause, and are simply attributing to 'a fault with Apple' on the grounds that other people who are not using your hardware also have wifi problems.

Use your noodle and don't jump to conclusions. That's what everyone is trying to tell you here.

Oh, and BTW, I have 10.7.3 and have NO wireless problems. So what's the difference btw your computer and mine, aside from the hardware?