I'll illustrate it with my experience yesterday. I finally got around to replacing the alternator on my '95 Ford pickup yesterday. While I had the belt off, I didn't bother to check the condition of my tensioner pulley. So with what was a 15 minute repair, I was off to the gas station to top off the tank and go for a short ride.
Three miles later I round a corner only to hear a thump as I round it. A quick check of my gauges, and I immediately realized that I threw my belt. I pull over, call my wife and make a quick call to the local O'Reilly to see if they have my belt. They do. Deb pulls up, takes me to the auto parts store, I get the belt, we return, I install it and shut the hood. Well..sort of. It will only catch the safety latch. So now during the three mile drive home I am praying that I don't go into a strong wind, or some boy racer passes me in the opposite lane at breakneck speed. This has happened before so I know the drill.
I am now reaching through the grill with my 1/4"ratchet a quarter turn at a time to release the latch assembly. When I say I know the drill, I should have said on to rookie mistake number two. When this happened before, inexplicably the latch bolts worked loose and misaligned enough that the hood would neither open nor close. Now, fifteen years ago, did I bother to maybe put a little blue thread locker on the bolts? Of course not. That would have been 30 seconds more out of my time. I most certainly did this time.
So now, after FINALLY getting my hood back up and the latch aligned (and bolts now coated with blue threadlocker), I see what shredded the perfectly good belt. The pulley on my tensioner looked like it had been through a meat grinder (I guess the plastic just got brittle with age because I use the 3/8" drive hole that Ford was generous enough to cast into the tensioner assembly). Now I am BACK at O'Reilly for a pulley.
So to recap: Not doing a simple observation of my pulleys, and not using threadlocker on my hood latch bolts 15 yrs. ago turned a fifteen minute R&R into an afternoon. All from rookie mistakes. LESSON LEARNED!!!!!
Never thought about having threadlocker on hood latch bolts, I had the same problem and needed a new (well, used) latch to make it work again.
Funny thing about the tensioner pulley: I hate to admit it but I learned a lot about working on cars from the people that worked at O'Reillys and AutoZone. They (esp AutoZone) sometimes try to upsell me on a new tensioner or tensioner pulley when I'd change an alternator. I fell for it once, but after that I always spin the pulleys when the belt is removed to ensure they are working as they should. And, just last year, I had to change an idler pulley when it failed the test! So I guess it's a good thing they taught me to check the pulley.
My first stereo install in my 1986 VW GTI. Dash trimmed to make it look factory new, custom front to rear fader hidden in console cubby, wires soldered in place. The moment of truth, I turn the dial and glorious sound fills my garage. Except. I don’t have the key in the ignition, it’s in my pocket. I had wired the head unit to a permanent hot wire!
Don't feel bad. I helped a friend in high school install an amp. When he asked me if he should use the radio fuse for power is replied, "Sure. Should be fine." I think you can guess the results.