In Need of Tech Help, iMac Wifi Issues

Have you tried changing your DNS settings?

 

See if this thread is any help:
http://forums.macrumors.com/showthread.php?t=1207455&highlight=wifi

 

http://support.apple.com/kb/HT4628

Not sure it's mentioned in the support guide, but you might also see if wifi is at the top of the service order. Some even suggest removing the Bluetooth option.

 

I too had the same issue as you, with my iMac.

I disabled IPv6 since Comcast was sending IPv6 to my modem, disabling that on my Modem seems to have worked to resolve it.

 

Ian, I would begin by trying to find out if the problem is on the internet side (where your brother's use may be causing your problems) or on the wifi side of the router (where your brother's use should have no effect); try a temporary direct connection from the router to your Mac, both when your brother is online and when he is not.

Walls and electrical wiring can interfere with wifi; I have a friend who wasn't able to get a wifi signal in his living room, with his router in the den, and moving the router across the den solved his problem.

Good luck.

 

I had a similar issue in my house...my Mom's MacBook would not have internet intermittently at her desk. But, if we moved it anywhere else, it would reconnect.

I found that our neighbor's WiFi was actually interfering with here computer since she is on the far side of the house.

Try changing the channels on your router until you get a solid connection. That is what worked for me after being frustrated about it for a while.

 

As others have suggested, there are many things that can interfere with WiFi signals. You might also consider changing the wireless channel used by your router, as WesCole suggested.

You don't need "cleaner" or "maintenance" apps like CCleaner to keep your Mac running well, and some of these apps can do more harm than good. Some remove files/folders or unused languages or architectures, which does nothing more than free up some drive space, with the risk of deleting something important in the process.

These apps will not make your Mac run faster or more efficiently, since having stuff stored on a drive does not impact performance, unless you're running out of drive space. Some of these apps delete caches, which can hurt performance, rather than help it, since more system resources are used and performance suffers while each cache is being rebuilt.

Many of these tasks should only be done selectively to troubleshoot specific problems, not en masse as routine maintenance.

Mac OS X does a good job of taking care of itself, without the need for 3rd party software. Among other things, it has its own maintenance scripts that run silently in the background on a daily, weekly and monthly basis, without user intervention.

Five Mac maintenance myths​

Repairing permissions will have no effect whatsoever on your wireless issues. Some people repair, or recommend repairing permissions for situations where it isn't appropriate. Repairing permissions only addresses very specific issues. It is not a "cure all" or a general performance enhancer, and doesn't need to be done on a regular basis. It also doesn't address permissions problems with your files or 3rd party apps.

Five Mac maintenance myths
Repairing permissions: What you need to know
About Disk Utility's Repair Disk Permissions feature​

There are times when repairing permissions is appropriate. To do so, here are the instructions:

Repairing Disk Permissions​

If repairing permissions results in error messages, some of these messages can be ignored and should be no cause for concern.

Mac OS X: Disk Utility's Repair Disk Permissions messages that you can safely ignore​