Feb 07, 2010
An important lesson I learned about patience came at my own expense.
Long ago I needed to replace the alternator in my personal pickup truck. I was 20-something, brash, impatient, all-knowing, confident I could do the job in a half-hour or less. All it required was removing or loosening two bolts, unplugging the wiring harness and swapping the pulley from the old alternator to the new one. Piece of cake.
Veteran mechanics will note there is a step missing from the disassembly process: Disconnect the battery ground cable. I knew I should "kill" the vehicle's electrical system before doing any work on the primary electrical system, but I was in a hurry and confident I could get things done without that "extra" step. Besides, the battery cable bolts were corroded, would probably be hard to get loose, and I did I mention I was in a hurry?
Skipping that extra step cost me an extra trip to town and $125 for another new alternator. Somehow during the installation process the power lead made contact with the "first" new alternator's housing. The ensuing blue arc and loud "pop" seared forever into my brain the lesson, "Always kill a vehicle's electrical system before replacing a starter, alternator or any other primary electrical component."
After a quick trip to town and a check for $125 for the second new alternator of the day, I disconnected the battery ground cable before making further repairs.
Yes, alternators and starters can be replaced without disconnecting the battery ground wire. Some mechanics leave batteries connected but wrap the end of the alternator or starter's electrical lead with electrical tape to prevent accidental short circuits. Some mechanics are just plain less clumsy than I am, and make the repair without problems.
Me? I disconnect the battery.