Lately, my car has ocasionally had an issue where it completely goes black, no lights, no power windows, no cigarette lighter, and obviously no ability to start the engine; cant even get the solenoid to click. Heres the totally strange part: when it does this, I just have to open the hood, and measure the voltage across the battery terminals, and all the 12 volt power comes back. The moment I touch the two probes to the battery terminals, all the lights come back on, and I am able to start my engine perfectly fine. An hour or two later, the power disappears again and i have to do the same thing with a multimeter again. If it makes a difference, this is a 2004 GMC yukon.
My experience with vehicles I have owned over the years with this case I would say dirty connections on main battery leads remove your battery connections clean the battery posts to a shiny metal state also clean the inside of the cable ends to with the proper cleaning tool if this does not fix problem check other ends of cables for dirty connections.
Sounds like a grounding issue - the car isn't grounded correctly to the battery, so over time a charge builds up in the engine bay. Measuring voltage at the battery gives the charge somewhere to go (ground), so the engine goes back to normal.
The description is easy. Finding the bad ground connection - not so easy...