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Topic: Anti-Theft Alarm System 1978

in Forum: C3 Electrical


Anti-Theft Alarm System 1978

Posted: 8/21/16 8:38am Message 1 of 7
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Former Member
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Grosse Pointe Woods, MI - USA
Joined: 7/21/2016
Posts: 9
Vette(s): 1978 Corvette Coupe Base
Went to replace what I thought was a burned out dome light, new one still didnt work, checked fuse box and the fuse for the light was missing (presumably pulled by previous owner?), this fuse also controls all the interior lights, clock, and cigarette lighter, all of which did not work.

So I replaced the fuse with the proper 20 amp fuse and everything worked, all lights, clock, cigarette lighter...  and

the stupid anti-theft alarm, beeping beeping beeping

and I could not get it to stop, tried the key on the door, started the car, opened and reclosed all the doors and hood.......

anyone have an issue like this and what are possible solutions...  i would even just cut the wire to the beeper if I could get to it.. its buried in the front wheel fender...

for now I live without interior lights and clock and cigarette lighter


1978 standard



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Re: Anti-Theft Alarm System 1978

Posted: 8/21/16 1:45pm Message 2 of 7
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Dunedin, FL - USA
Joined: 3/21/2006
Posts: 262
Vette(s): 1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.

Hello and good luck.

I pulled the + wire from the "BEEPING HORN" on my Vette and had no more problem.Of course it was a bit of a chore to get my hand under the brake booster to get to the plug on the horn,however a little patience and she was free from the annoying beeping.
as I said Good Luck..             nosal1           Sal C



Re: Anti-Theft Alarm System 1978

Posted: 8/21/16 3:40pm Message 3 of 7
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Overland Park, KS - USA
Joined: 7/9/2003
Posts: 916
Vette(s): 1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day. 2023 Accelerate Yellow HTC Stingray
  lt could be one of several things. The door switches or the hood switch could need adjusting , the alarm switch itself could be defective , or there could be a short between the switch and ground.


1973 L-82 4 spd

Re: Anti-Theft Alarm System 1978

Posted: 8/21/16 7:25pm Message 4 of 7
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Former Member
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Grosse Pointe Woods, MI - USA
Joined: 7/21/2016
Posts: 9
Vette(s): 1978 Corvette Coupe Base
ok, i found the horn, at there is a yellow and orangish wire running to the horn, one appears just to be screwed to the bracket as a ground and the other is connected to the horn...

what i've read, and not sure if this is true, that even if I simple remove the wire and the horn no longer sounds, the relays will possibly still be sending the signal to the horn and will drain the battery...  correct?




Re: Anti-Theft Alarm System 1978

Posted: 8/22/16 1:13am Message 5 of 7
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Former Member
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Dunedin, FL - USA
Joined: 3/21/2006
Posts: 262
Vette(s): 1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.
Orangish wire should be the + line and power to only the horn.If you disconnect the orange wire then you have cut off power to horn no matter about ground wire as it does not have power as it a ground and will not conduct power or affect the relays.
      NOSAL!           Sal C




Re: Anti-Theft Alarm System 1978

Posted: 8/22/16 1:13am Message 6 of 7
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Former Member
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Dunedin, FL - USA
Joined: 3/21/2006
Posts: 262
Vette(s): 1980 Corvette Torch Red with Gold metallic 370HP/350 CU.IN.Turbo 350 w/shift kit.Originally CA.Car with 305 CU.IN.
Orangish wire should be the + line and power to only the horn.If you disconnect the orange wire then you have cut off power to horn no matter about ground wire as it does not have power as it a ground and will not conduct power or affect the relays.
      NOSAL!           Sal C




Re: Anti-Theft Alarm System 1978

Posted: 9/2/16 8:12pm Message 7 of 7
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Charlottesville, VA - USA
Joined: 9/3/2010
Posts: 104
Vette(s): 1978 Silver Anniversary L82 Previously: 1965 300hp Coupe in 1967. 1967 435hp Coupe in 1968-70. 1969 350hp T-top w/ac and all power options.

Hi LSGoose, Cutting the power wire to the horn will stop the beeping, but if the alarm is triggered, the relay and flasher will still be powered. If left this way, the battery will have a higher than normal drain. My "solution" on a previous '78 was to use a battery disconnect whenever leaving the car for more than a day or two, which was not very convenient. Another solution is to disconnect the anti-theft relay in the console. The relay has 5 wires - Black, Orange, Yellow, Lt. Blue and Dk. Blue/White.

Make it stop!




Joe T

in Forum: C3 Electrical


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