1976 Year Vette

The alarm is activated/de-activated with the key switch in the fender. All it is is a horn "beep-beep-beep-beep".
The two pin switches at the front of the door/hinge pillar are for the courtesy lights...they are not part of the alarm
The two pin switches at the rear of the door, at the lock pillar, are for the alarm, as is the one under the hood.
When the key switch is turned "On", it allows the alarm circuit to be powered up, thru a relay. When the door, or the hood is opened, the switch(s) provide a ground for the relay, which then energizes a "flasher", which then beeps the horn. The alarm flasher is actually the same type flasher that is used for your 4-way hazard lights.
To test it, just roll the windows down, and close the hood and both doors. Then turn the key-switch in the fender. Then, reach thru the open window, and open the driver door. The alarm horn should start beeping. If not, try the pass side door, then open the hood.
If it does not work at all, then there are several things to check, including fuses, wiring, the relay, and the flasher. The relay and flasher are in in the pass side rear storage compartment, under the storage box. Adams' Apple2008-03-30 07:34:14

Cool thanks for the info. I just tried it and nothing happened, so something is wrong. I am going to trace it out and find the problem.

Vertical is off, Horizontal is on.
Unless the switch has been removed, and replaced in the wrong orientation.
Don't be discouraged, or puzzled if it doesn't work...most of them have been disabled, or removed over the years. It is a super simple system, so it can be fixed.

The systems are all pretty much the same, with some minor wiring differences, the location of the alarm horn, and the addition of switches for the T-tops on the later cars('78>).
I'll look to see if I have a simple wiring diagram for the system somewhere...I think I do. The alarm system is not included in any of the wiring diagrams I have here. It IS in the factory service manual tho, I think. I'll see what I have, and I'll post a schematic later.

I was wondering were the hood pin is located on a '76? I have a couple of wires with wire nuts (no braket with a couple of holes) on them in almost the center of the rear of the engine firewall before the wipers at the top, I think this could be the location. When I activate my alarm I hear a muffled click noise near the rear driver's side wheel. I have been told the relay is located under the carpet behind the driver's seat. I have not looked under the storeage box yet. Thanks!

The hood alarm pin-switch is located right where you thought it was...apparently, yours is missing.
If there is a "clicking" noise when you activate the alarm, something is shorted out, somewhere, IF the alarm relay is engaging...it should only be "active" with one(or all) of the alarm pin-switches closed, as in if one of the doors is opened, etc.Adams' Apple2008-04-28 05:06:11

Thanks for the pic. That is were my pin is missing. I have found many suppliers that carry the pin and the alarm relay, but I have not found any type of bracket to hold the pin in place.

It's just a flat sheet-metal bracket, bent to 90 deg. Nothin real impressive...