With no advanced problems, the truck would not start. The lights were on their normal brightness but I did not even hear the solenoid clicking. I pulled the starter and Autozone checked it out and it was working normally.
I put the starter back in and when I was putting the battery (positive) back on, the starter began turning without the keys even in the ignition. I think that I put the heat shield on and it was making contact with the hot wire and the ignition wire. Tonight I will take off the shield and try it
again. But it still does not answer why it would not start yesterday. My
neighbor thought it could be a dead cell in the battery which would give the appearance of being fully charged but when placed under a load, it would not do anything. Any help out there?
Thanks,
Don

Did you try starting in both Park and Neutral? I think there is a starter relay under the hood too.

You just learned a lesson as well, dont mess with the electrical untill you disconnect the batt,
i learned the same on my firsy car
(70 dodge cornet) only i had to spend 2 days after replacing the starter finding and replacing a fusable link that i blew changing the starter.

dirty cables

1999 GMC Sierra 1500 Ext Cab (old body style) 305 (5.0 liter)

This weekend, I had similar problems. Turn the key; lights, radio, fuel pump, etc all power up. Try to start, and just clicking. I replaced the battery with a new one, and still the same thing. Then I discovered that the positive cable had considerable corrosion. Using baking soda and water, and a flathead screwdriver, I cleaned everything that I could down to bare metal on the cable connectors and bare lead on the side post. This did the trick. I had the old battery tested, and the guy at Checker said that it had a charge, but a shorted cell. So, even though I have the new battery and cleaned cables, I plan to replace the entire positive side cabling with new ones.

SunDog67

1999 GMC Sierra 1500 Ext Cab (old body style) 305 (5.0 liter)

2 days later: I started having the same problems again; would have to wiggle the positive side cable while my friend kept turning the key to finally get it to start. I replaced the positive side cables with new ones from the dealer and it started right up. Here are the GM part #'s and the before tax prices that I paid for new cables for my particular truck:

Positive:
# 12156900 $56.98
# 12157093 $47.58

Negative:
# 12156901 $26.90

Pretty expensive, but I'd rather go with oem on stuff like that. Also, the pricing above was from a Chevy dealership; the exact same cables (same part #'s) were 25% higher in price at the local GMC dealership!!!

Hope this helps!

SunDog67