HELP!

That's a good question!
Mine doesn't work either. I thought turning the key to the right in the door lock, sets the alarm. And if I opened the door without the key, the alarm would go off.
But it doesn't!
Sounds like we both need help on this one!

There are two basic areas of the alarm (beyond having bad door or hood contact switches) that cause the alarm to fail. One is the relay set in the rear compartment. Two is the horn itself. If you have good electrical connections to the relays and horn then the problem is going to be in either a relay that won't energize or a horn diaphram that is stuck. Most of the time, the problem is going to be in the horn itself since the relay is fairly well sealed. Unless you exercise the alarm system regularly, it will be a recurring problem in the horn. The only way I've found to restore operation with the horn in its well hidden location is to use a long dowel rod to gently assist the diaphram into motion. I'm sure this isn't a factory recommended technique, but it has done the job for me.

Also, let's not forget that the factory never intended these cars to be on the road as long as we've kept them there so things like the alarm system longevity were probably never forecast to be a long-range issue.

Gerry, Thanks for all the good information.
-------------- Doug

One of the first things I fixed was the alarm on my 80 Vette when I got it. Actually I think it only partly fixed the lights won't flash, but thr horn goes off just fine. Check to be sure the horn is pulged in, mine wasen't. Also don't forget to check the fuse block and its fuse, I think its a 10 amp fuse. Alsi make sure the door buzzer is pluged into the fuse block and the wire coming from it is pluged into the fuse block. For some reason my alarm would not work with this unpluged. I actually took my horn out and cleaned it up. Its down low near the fire wall on the inside of the fender on drivers side. Actually I had to take off the side grill and reach up through the hole there to get it out. I rapidly found out mine was disconnected because the alarm switch for the hood was bad and would go off. The good news is there are only 3 such switched one for each door and one for the hood. Hope this helps.

Thanks Glenn

PS hope your limber because the fuse block is a B**ch to get at. I have a layout of the fuse block for my 80 don't know if its the same for yours but if you need it E-Mail me and I'll scan it and send it back as a JPG immage.

All the above and...

On a 78, as stated above only the two doors and the hood have the alarm points. There is no ignition interrupt on your 78, so it comes down to what has been mentioned already, I'll add a few more things to check..

Check the door locks, there is a "C" type clip that has the alarm acutator connected to it, if it is not positioned correctly the alarm will never set. Be sure you interior lights work quickly when you open the door, the alarm goes through this switch.

Check the grounds,, check the grounds, yes check for bad or poor connections at every ground in the circuit, as well as the horn. The alarm system has a 10 amp fuse, plus it relies on the 10 amp radio fuse too.

If all the connections are good, grounds are making good contact, and the fuses are good then depending on where your control module is, this could be in the center console, or in the rear compartment in back of the passagers seat, may need the spade lugs cleaned or you may even need to replace this module. There isn't a whole lot to the older alarms, just a few wires, switches and a horn :)

good luck, a deep breath once in awhile helps too.

Bud

Thanks, Mr milkman and also Bud for that information.
-
-Doug

When I got my 1980, the alarm would always go off if I tried to set it. Couldn't figure out why. I checked all the switches. The doors, the hood, all worked.

Then I found out about the "other" switches. The T-Tops have each have a switch. It is inside the hole where the rear latching pin goes into the car. Press in there and you will find a spring loaded switch.

The problem is the locking pins were not going into the car far enough to activate the pins. When you set the alarm, it had an open switch and would go off.

Take a look at the locking pins on the T-tops. There is a small cut in them to allow a screwdriver to be inserted. You can then turn them in or out to set the travel of the pins.

CAUTION!! Too far out will allow you to put the top on the car, but not get it back off !! Also, too far out and they will come off.

Since I adjusted my pins a year ago, they system has worked just fine.

Red Hot is on to something here BUT be very very careful. The tips of the t-top rods can sieze over the years. Do not lay on them when trying to get them loose. They will break. Trust me. Been there, done that. If you cannot get them to turn using moderate pressure on the screwdriver, stand off and see if you can loosen them up with WD-40 or the equivalent. You can also attempt to make adjustments on the switches/latches on the halo panel. There is a little bit of adjustment there. Do not remove both of the trim screws at the same time. If you do, the tapping plate behind the latch inside the halo panel will drop to the bottom of the car. If that happens, the only way to get them out is to begin removing interior trim panels.

I have an alarm problem also. I was having my 81 NCRS Judged Last Weekend at the 5th Annual NCRS Mardi Gras Meet (won Top Flight!) and the alarm only worked on the passenger T Top. Does anyone have any idea where I might start troubleshooting with a symptom like this?