Headlight related beeping/dinging
 

So today I finally was able to buy the Mustang I've been saving for. It's a fantastic 1999 in what seems to be perfect condition. No prior crashes, recall issues worked out, new battery and whatnot.

I picked the car up tonight around 9pm, started her up, turned on the headlights and it began. An incredibly persistent beeping almost dinging sound with almost no delay between them. It doesn't ding a few times and stop or even pause, it went on the whole 20 minute drive.

After getting home, I decided to do a little bit of investigative work and was able to throw down the following information...

With the headlights on:
-The beeping persists through jingling the key.
-The beeping persists with the key in any position.
-The beeping persists with the key removed. (Which, is really sort of a given)
-The beeping doesn't care how many times I close my doors, or the ferocity of the closing.

Headlights off:
No dinging at all.

I'm sure I'm forgetting things, but I've got a terrible headache, feel free to ask anything and I will do my best to help you help me.

In return, here is a bunny, with what looks like a pancake on it's head.
:icon_bunny:

But aside from that, I LOVE the car =D

sounds like it could be something with the door switch or the key (can you pull the key out of the ignition with it in the ON position)

I just checked it out and my key cannot be pulled from the ignition while in the on position. A door sensor may make sense, considering it's the same sound my other car makes door open/headlights on.

does your interior light work correctly?

I have the same problem
 

My key can be pulled out of the ignition and I have a consistent chiming sound when my headlights are on. My dome light also stays on no matter if I mess with the switch and try and turn it off. Any ideas?

The door switch will be easier to try first before pulling the column apart, the key cylinder can wear out and not make contact as well thinking your have the lights on with the key off.