1981 SC Random Horn Gremlin
 

I've owned my '81 SC for 13 years. Garage kept, driven occasionally otherwise on a Battery Tender. The last couple of weeks I've heard a horn going off something like 8 times, always the middle of the night! I've thought it to be a neighbors car alarm. This evening I was able to catch the sound and found it coming from my garage.
Never had a problem or had this happen before. My question: Is there an O.E. Alarm on the 81's that I didn't know about before? It is NOT the standard city horn on the wheel either. Does not appear to be an aftermarket unit installed anywhere either. Anyone have an idea or?:confused:

Is there a keyed lock slot on the inside of your drivers door jamb?
(On the door itself, not the body pilar/jamb.)
If so, you have the factory alarm.
The guts are located in the pack/pinion nook.
Bill K

Im having this same issue on my 1986 Targa...and yes, I do have that alarm key slot in my door jamb, and no, I dont have a key.

Any ideas?

I’d check on the age and condition of your battery. This problem is consistent with a weak battery and voltage fluctuation in older aftermarket alarm systems. Module is likely detecting a voltage drop and its triggering an alarm, this is how the system works when an interior light turns on…it set off the alarm. Your battery tender might be deflective too, but check the connections on both with multimeter.