[Gmecm] Welding vs. computers

[william meszko]

Doug,
   
  To be safe, turn off ign., safer yet, disconnect negative battery cable. If worried about the loss of capacitance the battery provides, connect the negative terminal just removed from the battery to the positive terminal with a clip lead. 
   
  Reasoning: Small glitches which don't have enough energy to destroy electronics in themselves can start an avalanche of sorts, with the almost unlimited energy available from the battery finishing the job. Tantalum capacitors fail explosively by this mechanism. Also any integrated circuit which has any pin raised more than .7 volts above the supply pin potential, or lowered .7 volts below the ground pin potential is at risk for latch-up. A latched-up IC is in a state of attempting to crow-bar its supply to ground, which is bad for both the supply and the IC.
  Of course, disconnecting the battery won't save the wiring harness if one tries to use the O2 sensor's ground lead to return welding current from the exhaust system to the car body, so the other suggestions you've received are even more important, IMHO. 
   
  Bill Meszko
  Fort Worth

Rexdina at aol.com wrote:
  Doug, I think your thinking on the battery disconnected/not disconnected is 
well founded. However, and there's always a however in electronics, some 
electric welders might be used in the negative polarity mode. That might explain 
what you've been told. Wish I could remember all the electronics I've 
forgotten. Then, maybe I could give you a more complete answer.
Harry
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