Okay, it's not a big problem - just a matter of curiosity. Here's what happened; My buddy called me up - he doesn't even have a descent set of wrenches and wanted to come over and change the serpentine belt on his mini van (an old, p.o.s. Dodge Caravan) Fine. I had him put a wrench on the tensioner (so that he'd bust his knuckles, not me) and pull toward the front of the vehicle to take tension off of the belt while I slipped the belt off of one of the pulleys. I removed the old belt, routed the new one over all of the pulleys but one, had him take the tension off again and slipped the new belt onto the last pulley. Job done. We try to start the car and it doesn't start. It cranks over just fine, but won't start. We scratch our heads, wiggle wires, and curse a lot - turning the key after every scratch, wiggle, and curse to see if it will start. Finally my buddy (vehicle owner) turns the key 5 times to have the dash board lights flash a code at him. He then goes in the house to call a parts store and see if they have a code book and will look up the codes for him. While he's calling, I'm grasping at straws and I wonder if it's possible that when taking the tension off of the belt tensioner we had tightened the bolt through the middle of the tensioner's pulley causing it to be too stiff causing the belt to not turn freely enough to start. He says not possible. (He also says that was not really a bolt, but just a bolt head on a welded stud - I don't know if that's right how do they get the pulley on the tensioner if that were true?) Anyway - I try to back that bolt off just in case - the wrench moves 2 or 3 mm. I try the key again - no start. I decide to turn the headlights on to see if they stay bright, go dim, or shut off when I try starting. While I'm trying to remember what the headlight test is supposed to tell me, the car starts. I let it run for a minute, shut the headlights off, shut the car off and started it again (no headlights). Everything seems fine and the car starts normally. It's driving us nuts that we don't know a) why it wouldn't start or b) why it did start. What in the world happened?