Re-wire alarm switch?
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
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From: Hudson Falls, N.Y. 76 Vette Modified L-48
Re-wire alarm switch?
Here’s an off driving season question…my 76 has a alarm key switch on the body, drivers side. The previous owner told me he replaced parts and attempted to make it work, but was unsuccessful…could I wire my HEI ignition power wire thru that switch to turn off the ability to start the vehicle…I mean as an anti-theft function?
Not a big deal…just curious if it would work…thanks
Not a big deal…just curious if it would work…thanks
CF Veteran
Joined: Aug 2005
Posts: 1,429
Likes: 19
From: Northern CA
St. Jude Donor '10-'12, '25
I was thinking about doing the same thing on my 76'. The only problem I see is with the anti-theft switch. Is this a mechanical switch... when turning the key does it open or close the contacts? If so, you shouldn't have a problem. Another problem would be the amperage rating of the switch. Do you know the current draw from the HEI ignition power? If it's to high you could burn up the switch. 
How were you going to wire this?
How were you going to wire this?
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
These are all good questions to consider, hence the post...mine is a mechanical switch...like a door lock, and I can only assume on/off...I don't have any idea of current draw on the HEI power wire, but being it is a such small wire, I can't imagine there being a high amp draw...as far as a battery disconnect, you would have to rig up some kind of high amperage relay system as I am absolutely sure that switch wouldn't handle battery power...
Maybe someone will jump in that has done this....we'll see..
Maybe someone will jump in that has done this....we'll see..
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Additionally...my thoughts were to extend the HEI wire to the switch and back to the distributor...turning switch on the fender would drop the voltage to the distributor...the engine would turn over, but you'd get no coil spark...no start...the vehicle would appear normal but no start...and in reference to the battery switch, with my option, there would be no effect on clock, radio station memory, etc...
It sounds like an easy Saturday afternoon type of project, again, maybe someone will chime in that has done this...
It sounds like an easy Saturday afternoon type of project, again, maybe someone will chime in that has done this...
Instructor
Joined: Mar 2003
Posts: 195
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From: Eagle Wi
I took one of those switches apart once. It is a simple make / break contact type switch. An internal contact strip simply rotates to brisge two contact points that align with the external wire connections.
If I remember correctly it would be sufficient to use on the 12V supply wire to the HEI. Someone suggested using it as a battery cutoff and there is no way it has that type of current capacity.
If I remember correctly it would be sufficient to use on the 12V supply wire to the HEI. Someone suggested using it as a battery cutoff and there is no way it has that type of current capacity.
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
Likes: 0
From: Hudson Falls, N.Y. 76 Vette Modified L-48
Originally Posted by ManFromEagle
If I remember correctly it would be sufficient to use on the 12V supply wire to the HEI. Someone suggested using it as a battery cutoff and there is no way it has that type of current capacity.
...not that I live in a high crime area, it would just be nice to foil the bad guys if they were eye-ballin' my beauty...before the got to her.Thanks again...I'm sure the other guys will check this post...
Heel & Toe
Joined: Dec 2003
Posts: 20
Likes: 0
From: Livonia MI
I wired my 77 factory alarm to a starter kill.
I purchased a 5 pin 40amp relay. I used a 3m t-tap to splice into the yellow wire from the factory alarm relay. When the alarm is tripped this wire switches to a ground -- you may have to probe if the wire color is different. I wired the relay near the factory alarm relay which is right below the shifter assembly. The only wires you have to cut are from the neutral safety switch which can be replaced if you wanted to return to stock.
I cut the purple wire from the neutral safety switch and connected each end to terminals 87 and 87a. I tapped into a constant 12v (lighter) and connected that to terminal 86. I connected the tapped line from the yellow wire from the factory alarm to terminal 85. Terminal 30 is left open.
The relay is only switched when the alarm is tripped and if it fails the car will start and not leave you stranded.
I purchased a 5 pin 40amp relay. I used a 3m t-tap to splice into the yellow wire from the factory alarm relay. When the alarm is tripped this wire switches to a ground -- you may have to probe if the wire color is different. I wired the relay near the factory alarm relay which is right below the shifter assembly. The only wires you have to cut are from the neutral safety switch which can be replaced if you wanted to return to stock.
I cut the purple wire from the neutral safety switch and connected each end to terminals 87 and 87a. I tapped into a constant 12v (lighter) and connected that to terminal 86. I connected the tapped line from the yellow wire from the factory alarm to terminal 85. Terminal 30 is left open.
The relay is only switched when the alarm is tripped and if it fails the car will start and not leave you stranded.
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Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
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From: Hudson Falls, N.Y. 76 Vette Modified L-48
Thanks for all the info, guys...but I have been forwarned by the previous owner to not mess with this car's alarm system, as he apparently did some kind of damage "bubba"-ing at it...so I figure a different route to stop the car from starting is the best way..just removing the potential for it to start is my best bet, and the HEI wire is the easiest and quickest route as long as it doesn't cause normal running problems...I guess that is my only question..will I lose needed amperage to the distributor if I extend that power wire...causing problems?
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
I have hard of guys grounding the distributor +ve wire to prevent hotwiring. This works well. The thinking there is that a thief can bypass an open distributor +ve by running a wire from the starter +ve, so by grounding it the distributor will never see the voltage.
Problems with this: ignition fuse will blow if trying to start the car with the distibutor +ve grounded. Also if a thief runs a +ve bypass he is basically connecting your battery positive straight to ground which equals melted wire & possible damage to battery & car. I suppose that is still better than losing your car
Instead of opening the distributor +ve wire the distributor 'trigger' wire can be open circuited. I'm talkin bout the wire that carries the signal to the coil. A thief can run a bypass wire to the +ve but it it won't make a difference.
Problems with this: its easy to find since this trigger wire is only 6 inches long and runs from the base of the distributor to the plug. If you have an aftermarket ignition module it is a lot easier to hide.
Problems with this: ignition fuse will blow if trying to start the car with the distibutor +ve grounded. Also if a thief runs a +ve bypass he is basically connecting your battery positive straight to ground which equals melted wire & possible damage to battery & car. I suppose that is still better than losing your car
Instead of opening the distributor +ve wire the distributor 'trigger' wire can be open circuited. I'm talkin bout the wire that carries the signal to the coil. A thief can run a bypass wire to the +ve but it it won't make a difference.
Problems with this: its easy to find since this trigger wire is only 6 inches long and runs from the base of the distributor to the plug. If you have an aftermarket ignition module it is a lot easier to hide.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
Originally Posted by kb2fzq
will I lose needed amperage to the distributor if I extend that power wire...causing problems?
Thread Starter
Burning Brakes
Joined: Aug 2005
Posts: 1,126
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From: Hudson Falls, N.Y. 76 Vette Modified L-48
Well..my thoery?? If a thief wants it bad enough, he'll get it one way or another...I am just trying to make it so that it isn't a cake walk...
OK, good advise from all of you...thank you
OK, good advise from all of you...thank you
Instructor
Joined: Jan 2005
Posts: 165
Likes: 0
From: Hobart Ind, near chicago
Originally Posted by ManFromEagle
I took one of those switches apart once. It is a simple make / break contact type switch. An internal contact strip simply rotates to brisge two contact points that align with the external wire connections.
If I remember correctly it would be sufficient to use on the 12V supply wire to the HEI. Someone suggested using it as a battery cutoff and there is no way it has that type of current capacity.
If I remember correctly it would be sufficient to use on the 12V supply wire to the HEI. Someone suggested using it as a battery cutoff and there is no way it has that type of current capacity.
Racer
Joined: Oct 2005
Posts: 251
Likes: 0
From: Grand-Falls New Brunswick
I think it is a good idea to cut the distributor but you should go through a relay just the same so the distributor isn't running through that cylinder switch in the fender because i have mine apart on my 74 and they are a very primitive set-up.