1975 factory alarm
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
I can't find a troubleshooting guide but you should be able to puzzle it out...
Start at the alarm horn, jumper 12 volts and a ground and confirm that it works.
Next go to the key switch in the fender and confirm 12 volts there and that you have continuity when the switch is turned 90 degrees.
From there check for 12 volts and a good ground at the anti theft relay.
Here's a basic schematic.
You may also have this switch which protects the alarm key cylinder.
The on line 75 schematic has no information about your alarm.
http://www.vetteprojects.com/bmv/mis...tte%201975.pdf
The 77 on line schematic has a diagram in it.
http://www.vetteprojects.com/bmv/mis...tte%201977.pdf
The relay and flasher are behind the passenger seat.
Do some testing and post back someone will walk you through it.
Regards, Pete.
Start at the alarm horn, jumper 12 volts and a ground and confirm that it works.
Next go to the key switch in the fender and confirm 12 volts there and that you have continuity when the switch is turned 90 degrees.
From there check for 12 volts and a good ground at the anti theft relay.
Here's a basic schematic.
You may also have this switch which protects the alarm key cylinder.
The on line 75 schematic has no information about your alarm.
http://www.vetteprojects.com/bmv/mis...tte%201975.pdf
The 77 on line schematic has a diagram in it.
http://www.vetteprojects.com/bmv/mis...tte%201977.pdf
The relay and flasher are behind the passenger seat.
Do some testing and post back someone will walk you through it.
Regards, Pete.
Last edited by Peterbuilt; Mar 26, 2013 at 04:39 PM.
Advanced
Joined: Jul 2007
Posts: 72
Likes: 2
I have repaired the alarm system on both my own 74' and my son's 74' and in both cases it was a bad key switch. You can jumper the switch terminals on the car and if the horn blows you know
the switch is bad (Note: to run this test you will need the hood or a door open).
the switch is bad (Note: to run this test you will need the hood or a door open).
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
I have repaired the alarm system on both my own 74' and my son's 74' and in both cases it was a bad key switch. You can jumper the switch terminals on the car and if the horn blows you know
the switch is bad (Note: to run this test you will need the hood or a door open).
the switch is bad (Note: to run this test you will need the hood or a door open).
Thread Starter
Le Mans Master
Joined: Aug 2001
Posts: 6,333
Likes: 1,311
C3 of Year Finalist (stock) 2019
C2 of Year Finalist (stock) 2019
I can't find a troubleshooting guide but you should be able to puzzle it out...
Start at the alarm horn, jumper 12 volts and a ground and confirm that it works.
Next go to the key switch in the fender and confirm 12 volts there and that you have continuity when the switch is turned 90 degrees.
From there check for 12 volts and a good ground at the anti theft relay.
Here's a basic schematic.
You may also have this switch which protects the alarm key cylinder.
The on line 75 schematic has no information about your alarm.
http://www.vetteprojects.com/bmv/mis...tte%201975.pdf
The 77 on line schematic has a diagram in it.
http://www.vetteprojects.com/bmv/mis...tte%201977.pdf
The relay and flasher are behind the passenger seat.
Do some testing and post back someone will walk you through it.
Regards, Pete.
Start at the alarm horn, jumper 12 volts and a ground and confirm that it works.
Next go to the key switch in the fender and confirm 12 volts there and that you have continuity when the switch is turned 90 degrees.
From there check for 12 volts and a good ground at the anti theft relay.
Here's a basic schematic.
You may also have this switch which protects the alarm key cylinder.
The on line 75 schematic has no information about your alarm.
http://www.vetteprojects.com/bmv/mis...tte%201975.pdf
The 77 on line schematic has a diagram in it.
http://www.vetteprojects.com/bmv/mis...tte%201977.pdf
The relay and flasher are behind the passenger seat.
Do some testing and post back someone will walk you through it.
Regards, Pete.
EDIT Alarm is fixed
Last edited by cor66vette; Nov 6, 2013 at 07:07 PM. Reason: Alarm is fixed
