THIS VEHICLE HAD BEEN PARKED IN THE DRIVEWAY FROM 7:45 PM, (AUGUST 10, 2011). I WAS AWAKENED AT APPROX. 3:55 AM ON 8-10-2011 BY HEARING A MUFFLED BOOM. AT 4:00 AM (AUG. 11, 2011) I HEARD A LOUD BANG TYPE NOISE. I IMMEDIATELY GOT UP AND WENT TO INVESTIGATE. I WENT OUTSIDE AND FOUND MY 2004 TRAILBLAZER (EXT) ON FIRE FROM THE ENGINE BAY AND JUST BEGINNING TO FLAME INSIDE THE VEHICLE'S PASSENGER COMPARTMENT AT THE DASHBOARD..IT ONLY TOOK MINUTES BEFORE THE VEHICLE WAS FULLY INVOLVED. THE FIRE BEGAN IN THE ENGINE BAY. THE FIRE MARSHALL REPORT IS STILL PENDING AND I WAS INFORMED IT WOULD TAKE 6 TO 8 WEEKS BEFORE IT WAS AVAILABLE. APPROX. TWO TO THREE MONTHS PRIOR, I TOOK THE VEHICLE TO A REPAIR GARAGE TO FIX THE LOW BEAM HEADLIGHTS (THEY HAD FAILED AND CHANGING THE BULBS WAS NO HELP. IT TURNED OUT THAT IT WAS A FAILED RELAY, WHICH WAS REPLACED. IT WAS A COUPLE OF WEEKS LATER THAT I HAD TO REPLACE THE VEHICLE'S BATTERY AS IT HAD GONE DEAD AND WOULD NOT TAKE A CHARGE. THE OLD BATTERY WAS ABOUT THREE YEARS OLD. THERE WERE NO OTHER BATTERY/HEADLIGHT ISSUES AFTER THESE REPAIRS. NO TOOLS OR OTHER PARTS WERE DROPPED INTO THE ENGINE BAY, OR LEFT IN THE BAY. I WAS AN AIRCRAFT MECHANIC AND OLD HABITS OF KEEPING RACK OF MY TOOLS NEVER DIE AND ALL TOOLS USED WERE ACCOUNTED FOR. THE ROADS WERE DRY WHERE IT WAS DRIVEN THERE WAS NO RAIN AT THE HOUSE ALL NIGHT. I REPORTED THIS TO CHEVROLET THAT DAY. AS A RESULT OF THE FIRE, THE EAVES OF THE HOUSE OVER THE GARAGE CAUGHT FIRE, MY WIFE, SON A