My workhorse machine is a 2.5 GHz A1260 with 6GB RAM and an SSD swapped in for the optical drive. I love it, scratches and dings and all. I've lost track of how many times I've disassembled it, and it's missing a few screws.
"Try relpacing the ambient light sensor. Apple Part # 922-8353 for the left.
MacBook Pro 15"" (Model A1260) Left Ambient Light Sensor
Here's how to do it: MacBook Pro 15"" Core 2 Duo Models A1226 and A1260 Left Ambient Light Sensor Replacement
This sounds similar to the ""Narcoleptic Aluminum PowerBook Syndrome"". Symptoms include the PowerBook suddenly entering sleep mode, no matter what the battery level is or if it is plugged in. One cause is the ambient light sensing, and associated instruction set coding, with possible keyboard backlight and sleep light issues accompanying the so-called ""narcolepsy"". Another cause is the trackpad heat sensor monitoring the trackpad; system logs report ""Power Management received emergency overtemp signal. Going to sleep."" To correct this, service groups will often replace the motherboard or power converter, but the actual fix (depending on the model) for the first cause is to replace or remove the left or right ambient light sensors; and for the second cause, disconnect, remove, or replace the heat sensor, or the entire top case which holds the trackpad heat sensor. Alternatively, there are reports which detail success in removing certain sensor kernel extensions or rebuilding the kernel using the Darwin Open Source project after commenting out the relevant sleepSystem() call; though permanent solution of the sleep issue in this manner is little documented."
Funky .plist files can cause all sorts of goblins. Of course you have already set ""Computer sleep=Never"", ""Display Sleep=Never"", unchecked ""Put the hard disk to sleep when possible"", ""Slightly dim the display when using this power source"". (battery) and unchecked ""Automatically reduce brightness before display sleep"".
Delete:
com.apple.systempreferences.plist
If this answer is acceptable please return and mark it.
"Incidentally, have you checked that the spotlight search on the SSD may be so ""fast"" that the processor actually overheats? I have had that issue with an SSD installed into an A1260/Macbook Pro/Core 2 Duo. Overheating can cause shutdowns.
Update
ncidentally, have you checked if the spotlight search on the SSD could be so ""fast"" due to rapid data transactions with the SSD that the main logic board actually overheats? I have had that issue with an SSD installed into an A1260/Macbook Pro/Core 2 Duo. Overheating can cause shutdowns.
P.S. you can download temperature monitor programs for your Apple on the internet for free."
"Wow, it looks like there are some pretty knowledgeable replies to your issue here. All of the commonly associated issues have been addressed. That's great, that's why you should look here first.
One thing that you may not have tried, although you have had this poor thing in pieces more than together, and have likely either resolved or trashed the machine in the 2 years past. I had a similar issue with an iBook that I still have around here somewhere. Performed all of the recommended and some ""don't try this at home"" things too.
The solution, was neither obvious nor logical. Often Mac laptops, although super, have some issues with very tight space. One step that I took during my diagnosis and general parts swapping was to replace the bundle cable to the inverter, not the power side, the data side. In doing so I found the bundle to be in an awkward spot by the left hinge and slightly pinched. I replaced this wire bundle and found that the issue went away for some time.
Inevitably to start acting up again in a few months. My solution was to take a small piece of shrink tubing, heated it to slightly bind the wire bundle. Just long enough to get it through the hinge area. Then re-installed the cable in a slightly different location (I believe, just the other side of the hinge), and pushed a little further into the body end of the cable allowing for a bit more tension in the display end... wha-la! No more blinky display or odd shut-downs. It has been almost 1 year and sill going strong, with my niece at the helm (of course).
Since then, when I have seen this type of behavior I will immediately examine the wire bundle on the data side. Since pinching these very thin wires will change continuity of the wire itself, and while not causing the device to fail may cause some very odd behavior. Similar to issues such as ""micro-fracture"" of the etched surface of the board or ""Popped Capacitors"", it is much more simple to address and much less costly.
