Multiple Ignition Switch Failures

[scarecrow55]

I have a 1999 Suburban with a 5.7L Vortec engine, base model. I had the transmission rebuilt last year, it worked great then it started having shifting issues along with the engine shutting off while driving. All signs pointed to the ignition switch so I've swapped it out, 3 times now. The switch is only lasting me a couple of cranks and then won't crank the engine at all. My initial reaction was the manufacturer made bad parts so I upgraded to the AC Delco and it still did the same thing. I also changed the ignition housing (not the lock cylinder) during this process because I oops-ed and broke the plastic part that turns and actually engages the switch. I've tried looking around for this particular issue but all I end up finding is general ignition switch troubleshooting. Any thoughts or ideas on where to begin my search before I shell out $400 for 2hrs of diagnostics at the shop would be much appreciated.

 

[Schurkey]

What is the current draw of the starter solenoid, and ignition?

First Guess: Shorted wire causing massive current flow, burns the contacts in the ignition switch.

Have you pulled one of the failed switches apart to see what has failed in them? Then trace the circuit from that failure to the cause.

 

[Erik the Awful]

I have a 1999 Suburban with a 5.7L Vortec engine, base model. I had the transmission rebuilt last year, it worked great then it started having shifting issues along with the engine shutting off while driving.

The #1 cause is the side post terminals on the battery self-loosening. After re-tightening the terminals repeatedly on my '99 Suburban, I chopped off the side post terminals and went top post. Cured.

 

[scarecrow55]

So turns out the battery was just dying and the bad shifting was due to low transmission fluid. Fun times when you're advised that the two issues are linked. Thanks for the replies.