I've been having spotty ignition trouble and it's reached the point where the car wont even start. I'm going to try to describe this as best I can but it has me buggered so it might be kinda confusing. I turn the key to the ACC position, fine, interior lights stay on. Turn to run, sometimes everything goes dead. If I turn the car to ACC and turn on the headlights, everything goes dead. If I turn off the headlights and turn the key to OFF interior lights come on (Dome, door, etc.) but they start out dim then suddenly get normally bright. All at once, no warm up. If I turn the key to start, sometimes the starter solenoid will click, once I got a very weak crank, but it won't turn over. If the starter doesn't click, everything goes dead like when I try to turn on the headlights. I can turn the engine over by hand via breaker bar with moderate effort. Brand spanking new starter (or rebuilt anyway), fresh out of the box, tested at AZ before I took it home. battery reads decent voltage, a skosh below 12 if memory serves. I swear my car is possessed, but if anybody has any other ideas, I'd appreciate it.

EDIT: I have the service manual, so if you have some idea what circuit might be causing the trouble, I can look it up and test it.

Bad battery cables/connections or a bad battery. What does the voltage at the battery go to when you turn on enough stuff to make it go dead?

Yeah so I checked the positive and negative connections several times. Cuz this would be the third time that I didn't do that and almost bought a new starter except this time I actually did buy a new starter. I unscrewed the neg. battery connector, cleaned it up, now she starts beautifully, especially with the new starter that I ended up not needing. At least it was cheaper than when I replaced it last time since I was able to get the core charge back with the old starter. Problem solved. Except for the problem of me being a royal idiot over the same issue THREE times now...

third times a charm

hopefully there won't be a fourth

I just had a very similar situation occur yesterday. I tried to start my car yesterday morning. I switched the power to on, all interior lights came on like normal. When I went to crank it over all the power cut off. The entire car went dead and remained dead for several seconds. After a short wait, I tried it again. Same thing: First there was power, and as soon as I tried to crank it over all the power cut off. After reading this thread, I tried it one more time with the same results. Disconnected and cleaned the ground on the battery terminal. Now there is zero power at all. Nothing. Completely dead. Would VATS do this if it was going bad? I'm confused.

I'd be careful about throwing too much money at this problem unless you're sure it's not a battery connection problem. You can buy new studs to put on the battery cables, they're kinda stubborn but it can be done and it costs a whopping $5 to do. If the terminals are corroded, when you clean it off, the threads don't always make good contact. I have a van where the threads stripped completely when I removed the connector from the battery.

My 'maro is an '83 so I'm pretty sure I don't have a VATS system, but here's an article about it.

As expected, it was a connection problem. Instead of the negative side of the battery, it was the positive side. As soon as I cleaned it off and went to reconnect it, I heard the familiar sound of electricity arching and the relays clicking as I reconnected the battery terminal. Car started right up afterward.

Just to answer your question. Yea, the VATS would do it. But theres a really good way to tell, if the security light in your cluster comes on then goes out after a second or 2 or 3 then the security system is operating like it should, but if it stays on then its not detecting the right resistance from your key. Which could be the VATS module, your carbon block in your key, your ignition switch leafs inside the barrel, or it could be the wiring. Just for future reference. and its stupid because the Haynes service manual, doesnt say jack about the VATS system.....