I've got a '77 with factory installed alarm.. It hasn't worked since
I bought car 3 years ago.. Where can I get wiring diagram , so I can
find problem and get it functional again?? Have called GM Dealers and
GM's 800# and no one can help...Helm Publication has no info either.
Jeff

I don't know if the A.I.M. for your year would have wiring diagrams in it or not, but worth a look anyway. Also check either the Chiltons or Haynes repair manuals. If you don't have any of these, all three would make good additions to your garage library. And if all else fails contact Normand (aka NormVet80 - n_sauriol@hotmail.com), he seems to have wiring diagrams for everything!

Many folks disconnected these alarms because they were really troublesome. They would go off for no reason, usually at the wrong time, like 3AM. Mine has been disconnected by the PO for this reason.

I worked on my alarm until I was able to get it working again. It has worked very well. It's tripped by either door being opened, or the hood being opened. It will also go off if someone attempts to remove the switch that arms it. On a 75, the arming switch is located on the driver side, just in front of the door. I know that later models were actually relocated and the door lock then armed it. I don't know when this move was made. I pretty much know the wiring system on my 75, because I had to do a lot of work getting everything working again after I bought it. "Ecklers" makes excellent wiring diagrams and come Laminated 18" X 22" Size. I posted mine on the wall where I can easily refer to it whenever I am working on any of my wiring. Excellent investment at only 16 bucks. Using this diagram, I was able to trace down every switch, wire and connetion. Now, I won't lie to to you, if you need to replace any of the components on the alarm, it will probally not be cheap. I had to purchase a new key switch, because I didn't have the origial key and the arming switch was broken (it is also the same switch used in the headlight position switch). All together I spent around 100 dollars getting the alarm to work again on my 75. It may be wiser to invest in a up-to-date alarm system, but I wanted mine to be original and it does give me piece of mind. The alarm is simple and doesn't sound like any of today's alarm, so it has it's own sound and easy to distinguish from other alarms. If you need any more information, email me at bill0830@yahoo.com and I'll help out as much as possible.

The first thing you should check is if the horn is working. It is tight but get some long wires(with clips) and connect one to the ground and one to the positive terminal of the horn(you will have to remove the plastic connector from the horn and make contact with the metal part inside of the connector. Then apply these wires to a test light. Then arm the alarm and open each door and hood. If the test light comes on your wiring is OK. Now you have two choices, repair the horn, I did but it is not an easy job. Or search for a working horn, there are many different ones and they sound different if you are contemplating NCRS type judging.

Good Luck