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1977 Anti theft.

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Old 04-15-2018, 03:15 PM
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JillsVette
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Default 1977 Anti theft.

Finally got the interior in. Everything works took for a short drive last night. I am happy so Jill should be too we have an appointment for state inspection and 4 wheel alignment this coming week.
The driver door anti theft switch was unhooked so I reconnected and it seems to work ok.
the hood switch was bypassed and the two wires just spliced together. So I cut the splice to reconnect to the plunger switch and saw the plunger contacts are missing so I need a new switch. I consulted the factory GM manual that I have and it looks like the two wires are supposed to be connected in the same female spade connector.
since i cut the splice the interior light do not work when the door is opened. Reconnect the splice they work again.
Here is my question are these two wires supposed to be connected in the same female spade connector? And if so that will solve the interior light working when the door is opened but how does this work when connected to the hood switch. Im having a momentary lack of electrical circuit intelligence. Attached is a pic with the connector circled.

Matt
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Old 04-15-2018, 03:52 PM
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sparky77
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On my 77 there are two separate wires going to the switch one is above the other,Next time I go out there I will open the hood and see if the interior lights go on or if they stay off.

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Old 04-15-2018, 04:23 PM
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The hood switch has 2 spade connectors separated by plastic. One wire should land on each side. The switch is a normally closed contact, when the pin is pressed the switch would be in the open position. The switch shown is in it's closed position, Hood or door open.

The GM parts book lists the switch in two different Group numbers. Gr.2.195 part number 6258295 75-82 Switch Anti Theft Hood and Gr.11.950 part number 6258295 73-76 Switch Dr Ajar Warning Lamp, just to let you know that 73-76 door switches are the same switch.

On the late 77 the hood alarm switch and door courtesy light switch circuits are different. Each switch serves as its own path to ground in its normal state.



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Old 04-15-2018, 06:26 PM
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By them joining these two wires together....it is telling me that you have an issue with your door jamb switches or wiring at them or to them.

The under hood switch as you know is a tamper switch for your alarm system. The door jamb switch also have the wire for your interior lights and alarm system added to it.

By them splicing the wires for the under hood switch together...they are supplying a GROUND to your wiring.

With these two wires under the hood spliced together....it would cause your alarm system to always be triggered and blow the horn. Which may be why the the drivers side switch was disconnected.

DUB

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Old 04-15-2018, 08:29 PM
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Default door switch

Do you know of a source that has an online schematic that would show greater detail than the factory manual?
​​​​​​​maybe there is a pinched or cut wire under the hood.
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Old 04-15-2018, 09:24 PM
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Originally Posted by JillsVette View Post
Do you know of a source that has an online schematic that would show greater detail than the factory manual?
​​​​​​​maybe there is a pinched or cut wire under the hood.
Go to this link, click on it.. Then right click on it and select copy... Then open your paint program (on all computers) and paste it into a file.. save to your desktop.. You can then trace the wires in the paint program.. we use this almost every week.

http://repairs.willcoxcorvette.com/w...tic-tracer.png

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Old 04-16-2018, 05:56 AM
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Default ignition buzzer

Thank you for posting the schematic. Very helpful although I think this is for an early build 77. After reviewing all the circuits is it possible the ignition buzzer is the problem?
it will sound a very very low tone when the key is left in the ignition. Not sure about the seatbelt reminder side of the buzzer i dont have that wire plugged into a seat belt, should i run a jumper at the plug end?
thank you for all the help.

​​​​​​​matt
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Old 04-16-2018, 09:46 AM
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Is the picture you first posted from the 1977 Corvette Electrical Troubleshooting Manual?

Manual -https://www.ebay.com/itm/1977-CORVET...pYrVbK&vxp=mtr

It is the most accurate and in color for both early and late build 77. You may find some wire color differences for the late 77 but for the most part it is a very good manual printed by GM sometime in 1977.

On the buzzer, you can open it, but if you do be careful as there is a tiny wire soldered to a set of contacts (like old style points) from the coil. I lightly sanded the contacts on mine and it started working again.
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Old 04-16-2018, 09:45 PM
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Default ignition buzzer

Yes the first picture is from that exact book.
the 2 wire plug that goes into the warning buzzer maybe in backwards as it can go in either way. Possible that could be it.
as far as the interior lights, door switches are new. So if I was a betting type It would seem either the door mounted activated anti theft switch could be the issue....
​​​​​​​
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Old 04-17-2018, 08:01 AM
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Originally Posted by JillsVette View Post
Yes the first picture is from that exact book.
the 2 wire plug that goes into the warning buzzer maybe in backwards as it can go in either way. Possible that could be it.
as far as the interior lights, door switches are new. So if I was a betting type It would seem either the door mounted activated anti theft switch could be the issue....
​​​​​​​
About the plug, it is designed to attach to the buzzer in only one direction. At the plug you will see a #20 pink/black wire and a #14 orange wire. Turn to page 18 in the electrical troubleshooting manual. The #20 pink/black C122 & the #14 orange wire C122 are the same connector . The #14 orange wire circuit #40 is hot at all times, the #20 pink/black is one side of key in ignition switch contact and #20 black wire from the LH door jam switch is the other side of the key in ignition switch contact.
If you look at the plug you will see one side has an open slot (pink/black wire) and the male spade on the buzzer has a outward tang on the spade, the slot in the plug aligns with the tang.


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Old 04-17-2018, 06:50 PM
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I am kinda lost on what you are trying to fix. I though it was trying to get your interior lights to work properly when the door is opened and closed.

Now it seems you are working on the key warning buzzer...which has nothing directly to do with your interior lights. The only thing that have in common is the door jamb switch...which when the door is open....is providing a GROUND so the interior lights and key warning buzzer work IF the key is in the ignition. 'bmotojoe' described the circuit quite perfectly. SO using a voltmeter and an ohmmeter is needed to make sure the ground from your left door jamb switch is providing the ground to the terminal in your turn signal switch correctly..and then IF the contacts in your steering column are clean and doing their job and transferring that ground signal to your pink/black wire in your key warning buzzer.

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Old 04-18-2018, 07:14 AM
  #12  
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Default Internal Door switch

this is my 3rd attempt to answer.. computers are a royal pain in the dumpster.

I think the best way to revisit this is to fill me in on how the anti theft system works. I understand once armed the alarm will sound if the following are disturbed, either door, the hood is opened, or a force able entry through the driver door lock.
since replacing the under dash harness everything is now working except the hood anti theft switch was bypassed, these two wires were just crimped together. i cut the wires to reattach them to a new hood switch and now my interior lights will not work the driver side door is opened. So I bypassed the switch once again and all is good with the interior lights.

Here is what happens when I think I arm the anti theft using the driver door lock. If I lock the door before closing it there is no horn sound. I assume that the system is not activated because the key was not used to lock the door.
If I lock the driver door with the key inserted at the 6 o clock position and turn to the 3 o clock position the horn will sound and the only way to stop the horn is to turn the key back past the the 6 o clock position and to about the 7 o clock position and the horn will stop, the door is still locked so at this point I assume the anti theft is armed and waiting for a forced entry. if I turn the key to the 9 o clock position the door unlocks all is quiet. just to be clear the hood switch wires are still spliced together at this point.. If I cut the splice and follow the same arming procedure the horn does not sound.
Bmotojoe suggested there maybe a grounded circuit somewhere along the way. So I was thinking looking at the schematic provided by Willcox that just maybe it was the key buzzer providing a ground feedback because it does not sound right, it is very weak. Of course I could be wrong and it maybe the internal door switch at the door lock that is the problem...
Thank you for the help.

Matt and Jill.
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Old 04-18-2018, 02:49 PM
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Here is how I lock/unlock set and disable alarm on my late 77.



Try this,
Pull both LH & RH door switches. Detach wires from both door switches. Checking one side at a time continuity from the Dk blue/white stripe wire to the Dk blue/white stripe wire at the hood alarm switch, check this when your hood switch wires are separated (not crimped together or connected to the switch). Do you get continuity? These 3 wires are tied together on the 1977 troubleshooting manual drawing S1001 S=Splice. The C115 you see on the drawing is the engine side bulkhead connection and the circuit is numbered 263, on Mr. Willcox early 77 drawing it is numbered 976.

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Old 04-18-2018, 06:56 PM
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Originally Posted by JillsVette View Post

I think the best way to revisit this is to fill me in on how the anti theft system works. I understand once armed the alarm will sound if the following are disturbed, either door, the hood is opened, or a force able entry through the driver door lock.

You are CORRECT

since replacing the under dash harness everything is now working except the hood anti theft switch was bypassed, these two wires were just crimped together. i cut the wires to reattach them to a new hood switch and now my interior lights will not work the driver side door is opened. So I bypassed the switch once again and all is good with the interior lights.

YOUR PROBLEM IS STARTING HERE!

Here is what happens when I think I arm the anti theft using the driver door lock. If I lock the door before closing it there is no horn sound. I assume that the system is not activated because the key was not used to lock the door.

CORRECT!

If I lock the driver door with the key inserted at the 6 o clock position and turn to the 3 o clock position the horn will sound and the only way to stop the horn is to turn the key back past the the 6 o clock position and to about the 7 o clock position and the horn will stop, the door is still locked so at this point I assume the anti theft is armed and waiting for a forced entry. if I turn the key to the 9 o clock position the door unlocks all is quiet. just to be clear the hood switch wires are still spliced together at this point.. If I cut the splice and follow the same arming procedure the horn does not sound.

When you connect those two wires under your hood...you are basically 'telling' the alarm system that some one has opened your hood...and THAT is why the horn blows WHEN those two wires are connected and you try to arm the system. And when they are NOT connected... that switch under the hood is NOT a part of the tamper switch portion of the alarm system.

Bmotojoe suggested there maybe a grounded circuit somewhere along the way. So I was thinking looking at the schematic provided by Willcox that just maybe it was the key buzzer providing a ground feedback because it does not sound right, it is very weak. Of course I could be wrong and it maybe the internal door switch at the door lock that is the problem...
Thank you for the help.

Matt and Jill.
Matt and Jill,
As I wrote in one of my previous posts...your problem is at the jamb switch or its connections or the fact that you have a problem in the interior light circuit. It is hard to give you an answer that is 100% spot-on without being there and running tests,

What it will take from you is to use your ohmmeter and check the circuits that go to your left door jamb switch.

I AGREE that you may have a problem in a lack of ground (obviously) because when those two wires under your hood are joined....The wire that is going to your left door jamb switch that is one of those wires under your hood is NOW grounded...and thus....when the door is open...it now is allowing a ground path to complete the ground needed to make your interior lights work via your jamb switch.

If you look...you key warning buzzer has nothing to do with your alarm or interior light works like I wrote previously also.

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Old 04-19-2018, 12:38 AM
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Originally Posted by JillsVette View Post
Do you know of a source that has an online schematic that would show greater detail than the factory manual?
​​​maybe there is a pinched or cut wire under the hood.
I have a colored coded laminated schematic for my 78 made by Olsen Engineering. I see that Dr Rebuild's uses Olsen for his schematic that are both color-coded and includes part images. No doubt the factory guides are tedious and obtuse compared to what's available today.

http://shop.docrebuild.com/Late1977o...riverDoor.aspx
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Old 04-19-2018, 12:12 PM
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thanks guys I will pull the switches and get a continuity test with the under hood wires seperated.
I'll be back....
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Old 05-16-2018, 12:15 PM
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Default Wiring

Rereading all the suggestions I can agree the issue is where the hood switch is bypassed to make the interior light work. (Still Bypassed at this point) One thing I noticed is the heater motor runs all the time when the key is turned to the run position. Should the heater motor run all the time? The car has Factory AC which was disabled by the previous owner(s), a lot of parts missing. Maybe be a cut or pinched wire in this circuit someplace. I noticed in the wiring diagram the ground for the heater motor circuit is incorporated in the anti theft ground circuit. I haven't had a lot of time to really trace it out yet and do a continuity test with the door switches. Its not one of those imperative must fix things its just would like to make it right.

I'll get to it just going to take some time since summer is finally here.
thank you all

Matt
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Old 05-16-2018, 12:26 PM
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NO...the blower motor should not be running all the time. Especially if the ignition key is turned off.

Not knowing what has been done when the previous owner removed the A/C. It can be something easy to fix or something entirely different.

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Old 05-16-2018, 04:35 PM
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When the key is in the run position and the fan switch is down,(Off) the fan will still run at a low speed, there is no off completely. This is outlined in the 1977 Chevrolet Chassis Service Manual section 1A-5 Y series.

If your fan runs with the key off you have other issues.

From what I understand this was done to keep fresh air moving through the passenger cabin at all times, but if you're in A/C max mode the plenum door should be closed, kind of puts a kibosh to the fresh air theory.

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Old 05-16-2018, 06:53 PM
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Why don't you just remove all that useless garbage? Its not worth the time or money.
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