Hello. New here and this is my first Corvette, 89 coupe have had it about 9 months now. It has developed a problem with the alarm. I used the key fob to unlock the car. when I opened it the car the horns went off and no matter what i did they kept going off. I put the key in the ignition and the car started so I unplugged the horns. A couple days latter I started the car and after letting it run for a couple minutes I plugged the horns back in and all seemed ok. When I shut the car off and opened the door from the inside to get out The horns started going off again . With the horns unplugged the car locks and unlocks normally and starts right up. when I first get in the car I can here a ticking from under the dash somewhere. Probably the horn relay being energized. It times out after a couple minutes. I haven't tried opening the passenger door to see if it sets of the alarm ( just thought of that) Could the door contact switch be shorted out or any other ideas. Thanks for your help

 

Unlock the doors with the power switch before you get out.If you dont,the security light on the dash will remain frozen and armed,not blinking.

You can test this...open the door and observe the security light is flashing on the dash...then while the door is open,push the power door lock to LOCK and the security light should freeze.If it does,its arming itself.Use the power door lock to unlock and it should start flashing again,meaning its not armed anymore.


Also,try turning the door key holes with the door key to full lock then unlock,and make sure you take the keys out straight as possible.The keyholes inside the door have a switch.They corrode badly with age.If you turn the key to lock then unlock,and it doesnt disarm the system,theres a good chance the alarm sensor switch inside the keyhole is bad.

Try both doors...I once had a bad drivers door switch,had to unlock the passenger door to disarm the alarm until I got it fixed.

Watch the security light on the dash...when it flashes its not armed..if it stays frozen lit up,and you turning the door keys dont disarm it,theres a good chance one of the inside alarm switches is bad.

 

Hello, I have had my own frustrations with my '88 as well. My father passed away with cancer in Nov. 2001. He always said that his '88 would be mine. I was heart broken when my aunt bought it from my stepmother. But my aunt ended up realizing that I was my father's son and it should be mine.

Anyhow, so many things have gone wrong with it just from being a twenty year old car. I can't count the times it wouldn't start when I have been out somewhere. The computer has died. Then one day out of the blue, the alarm kept acting up. I was driving down the street on more than one occasion and the alarm sounded even though it was off.

It turned out to be a wire that runs from the door lock was faulty. The wire has to be connected or the alarm will sound.

This may or may not be your problem, but it resolved mine.

The only way to stop the alarm from sounding is with the door key in either door. If you try to shut it off with the door key and it doesn't shut off then the wire, like in my case, was faulty. I was turning the key but it didn't recognize that I was turning the door lock switch.

What a pain. You would think these cars would have clickers to turn off the alarm.

It should tell you the proper way to lock and unlock your car in your handbook. It does in mine.

I wouldn't unplug my horns for safety reasons.

 

yep the round key in the door is the only way to shut the alarm off

 

First off, to kill the horns during alarm= use the key in the door lock and turn to the unlock direction. Test both doors.
The problem may be with your aftermarket key-less entry. It has to fool the theft deterrent controller into thinking that the door was unlocked with the door key. It does this by sending a ground to that input on controller, at the correct time.
Read the info on "forced entry alarm" from my manual.
http://members.shaw.ca/dankai/Vats%20Electrical.pdf
That should shed some light on diagnosing, but I think you will also need to find out what model key-less entry and get the schematics for it, too.

 

thank you for your help. I will try and check it out today. I k-new someone had installed an aftermarket alarm and I have all the paperwork for it. I did not know that the corvette in 89 did not have a keyless entry.

 

Thanks, cycling the key in the door lock seems to have solved the problem. Next up is converting the ac to 134