I did a A500 swap on my car and having the same problem.

Did you figure out what the problem was?

After reviewing a lot of similar issues on here and other sites, I keep coming back to bad converter, or it being lock up at idle speeds.

You unplugged the center wire, which is 12v and should do it? I'm going to try that when I get home tonight.

Hope thats it.

If you figured it out, please post it on this thread.

Thanks!