1996 Subaru Legacy noise under dash

This time when she put the key in the ignition, it buzzed, when the key was halfway in, the buzzing stopped, and it started again when the key fully seated all the way into the ignition switch. The car would not start, not even crank, yet when she jumped it, it started, on the second attempt.

That mode accuator just has this muffled thump to it, as best as I can describe it. ZI watched it while it was making the noise, and it looks like it's trying to turn the attached white curved piece, but it's like it's stuck, as best as I can describe it guy. It's intermittent. What does it actually do, and does it need to be replaced? I don't think this would cause the car to not start, if it's AC related, right?

Yes, car does have anti-theft. The mode accuator makes the muffled thumping sound. The buzzing she heard the day the electronics went nuts is coming from under the dash, on the left side, so that is probably the interruptor you are talking about. Today the car did it again. Turned the key, no cranking, no clicking, absolutely nothing. All the electrical components came on, lights, radio, dashboard lights, etc, but no engine crank, or even a clicking, nothing. I went out and I disconnected both cables from the battery, waited about a minute, and reconnected the neg first, then when I reconnected the positive cable, the alarm didn't go off, as it usually does when you disconnect and reconnect the battery cables. I did this twice and it still didn't go off. I thought it strange. After I reconnected it she turned the key and it started. I also noticed that even when the alarm is off, when it is parked in the garage and the alarm is not necessary, the red light for the alarm still blinks, as if it is activated, and after you turn if off, to drive the car, the alarm light continues to blink as if it were still on. Do you think it is possible that the security system has some kind of electrical short or other problem that is causing all of this, because the noise coming from the mode accuator for the a/c is unrelated to the starting problem, it just happened at the same time. I think I am going to disable the alarm system and see what happens, because she had the car diagosed at a local auto parts store, and the only code it registered was cylinder 4 misfire, which we know it does, because it does this ocassionally when she drives on the interstate. You would think a problem like this would register a code, but it doesn't.

I promise not to bother you guys anymore with this, but does my theory that there could be a problem with the anti theft system make sense? When this happens, it's almost as if the system detects a theft of the vehicle and kills the ignition. Does this sound like something feasible?

Thanks guy. My daughter says there is one small thing that doesn't work on her a/c so that is probably the glitch in the mode accuator. Right now that isn't that big a deal. I will download the info for disabling the anti theft, and hopefully that will take care of the problem. Hopefully this didn't damage anything else related to the ignition system.

Thanks again for all of your feedback. Saved a lot of money in diagnostic fees, and since this probably wouldn't have shown up anyway, it would have been $90 wasted. I will certainly use you guys again if anything else happens with her car. I have a feeling I will be talking to you guys again in the not too distant future.