My car won t stop beeping! Help?!

I have a 1990 Honda Civic I ve had it for 4 years. First some background info on the beeping. When you turn the car off and leave the key in the ignition the car beeps and won t stop until you take the key out of the ignition. It s a simple 4 quick beeps about one second long occurring every other second. I assume it s a feature that prevents you from leaving your keys in the ignition. Cool makes sense. Ok so here s the problem. About 4 months ago it started doing that same beeping but not when the car was off and the key was left in the ignition but when I was driving. It would beep a few times then stop. It was a very occasional thing. Over the next 3 months the beeping happened more frequently and stayed beeping longer and finally about a month ago the beeping started every time I turn the car on and continues until I turn it off and remove the key. Over this month I ve just turned the music up loud enough to mask the beeps but it s a really loud annoying beep. I just want it to stop. Today while trying to figure out how to stop the beeping I discovered that if I open the driver door it stops. If the car is off and the key is in the ignition and beeping if I open the door the beeps stop but as soon as I close it they start again. Same with if the car is in accessory mode beeping away if I open the driver door suddenly the beeps stop but as soon as the door closes they start up again. Same if the car is running.

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