Chosen Solution
My MacBook Pro (late 2008) increasingly refuses to switch on - ie as if battery removed. I have tried every tip going. Sometimes it works sometimes not. Generally if used daily or put to sleep it’s fine, but if shut down overnight it’s dead. I have removed the keyboard connector from the motherboard and refitted, which worked yesterday. Did a clean install and it hung, rebooting at start up screen. Had to force shut down as it got too late. Today nothing. Tried removing the keyboard truck but no. Any thoughts? I’ve successfully powered up from power up terminals on the motherboard yesterday so not sure where the issue is. Maybe it’s just died! Got a new battery and replaced hard drive a couple of years ago. Backed up before I started.
@clive_d - If your wiped your system’s drive then we do have a problem ;-{ Do you have a spare USB thumb drive? If you do follow this guide to create a OS installer drive: How to create a bootable macOS Sierra installer drive from your iMac. Then boot up under it on your MacBook Pro so you can install a fresh copy of OS onto it. Let us know how it goes.
If your really convinced its your power button then try a keyboard/powerbutton replacement MacBook Pro 15" Unibody Teardown
