Computer overheats when connected to AC power

Question

I've noticed for awhile now that my MacBook Pro tends to get extremely hot when I use it for any length of time, such that it's uncomfortable to hold in my lap. I had thought it was somewhat normal, and got a new laptop stand to dissipate the excess heat, and hadn't really worried about it since (or noticed it, now that it was never directly on my legs). However, just recently I've noticed that not only is it still getting very hot (hot enough that I can't touch it!), but that that heat is coming through on the top as well, specifically the little strip of aluminum above the keyboard. I feel like this can't be a good sign, and the computer has crashed several times in the last few months, although not necessarily always in direct correlation to this issue, that I've noticed.
Furthermore, it seems that the overheating only happens when it's plugged in to AC power. When it's unplugged and I'm using it heavily, it stays reasonably cool, but if I plug it in, even if I don't use it at all but just let it sit around running the screensaver, it gets too hot to touch. And the final thing related to all of this, in the last couple of days, sometimes when I plug the power cable in to charge it it recognizes that it's getting AC power on the menu bar, but gives the message "Not Charging". Usually it starts charging eventually, like if I turn it off, or wiggle the magsafe plug a bit, but it's not consistent.
The MBP is a 2006 model, has had a new battery since December '09 (the excessive heat predates it), and has spent the last 2.5 years in London living off of 220V power, which the adapter should've been capable of handling just fine. So yeah, anyone ever had this happen to them? I'm worried there's something wrong with the power handling capabilities of my computer, and I'm not sure what could be done about that. Thanks!
-Jeff

Answer 1

Intel notebook computers tend to "feel" hot regardless of the brand, so it's important to base your definition of "too hot" on hard data and not how it feels to the touch. There are freeware programs that read the various sensors and report the actual temps. I like the Dashboard widget iStatPro, available here:
http://www.apple.com/downloads/dashboard/status/istatpro.html
The case bottom is designed as a heat sink so it will get hot. Apple says don't use these on a lap or a pillow/blanket/anything that blocks off the case bottom. Your getting a stand helps. I use a lapboard or a chill pad when I need to use my MBP while sitting.
There is also an exhaust vent along the hinge on the back panel. This area should not be blocked.
Another thing to check is to make certain that some background process is not in a "runaway" state and needlessly eating up processor cycles. That will raise temps. Find Activity Monitor in Applications > Utilities and launch it. If you've not used AM before, the "Show" field at the top of the window is set to "My Processes" by default. Change it to "All Processes" to get a realistic view of what's happening.
Have the computer "at idle," that is, no user apps running and Dashboard inactive. If you've used DashBoard that session, wait to run AM until after a restart. Click on the column header "%CPU" to rank processes' usage from highest to lowest. No single process should be using more than one digit of the cycles (under 10 percent--on mine it's more like 5).
If you see a process that's more than 10 percent, post its name hear and we can see if there is a safe way to limit its enthusiasm.