Rear Defrost 93 GA

The rear defrost is tempermental on my 93 GA - it has been for quite a long time. I can initially turn it on but it will shut off after a minute or so of city driving and the window is barely cleared of ice/fog. If I try to turn it back on again, it won't let me - indicator stays off! I can turn it on after approx 30 mins of driving. The manual says something about the time-out being different at higher speeds but even then it turns off pretty quickly. ANNOYING, especially during a snow storm. The power antenna mechanism busted years ago and I've disconnected it in the trunk. It used to jamb occasionally and the breaker in the fuse box would get quite hot. I've recently replaced this part but it didn't fix the problem. Anyone seen this problem or know of a fix for this?

I had the same problem...antenna and all and when the antenna was disconnected, my defroster would also kick off very quickly. You probably don't want to hear it, but when I replaced the antenna, it started working fine again.