I bought this car last year and just have gotten around to fixing some things.

I had a battery draw. Wasn't the courtesy/glove box lights. But it is on that fuse circuit so I figure its the alarm. So I did some digging around on it and I've got alot of problems.

#1. The alarm doesn't sound. Not sure if its the horn or something else. I'm working on testing the horn next to the brake booster. It does have +12V to it all the time as its supposed to. I haven't tested the relay yet either.

#2. The horn from the rear tire well is missing and the harness to it was clipped off and tie wrapped up.

#3. Only one of the two alarm harnesses in the drivers door was connected to the lock. The lock had some peices broken on it so I'm going to order new ones.

#4. All of my keys are aftermarket. I had some new GM keys cut at Home Depot but they don't work so well. Not sure if it was the cut or what. So I'm thinking about ordering all new locks for the doors and the ignition and just get it over with while I'm in there.

So my questions are:

- The horn is next to the brake booster is the ONLY alarm horn correct?

- What is the horn in the rear of the car for?

- Is there a company that will sell a complete lock kit for the ignition, doors, glove box, etc so they all work on only two keys?

- I'm probably going to have to order either an alarm relay or the horn in addition to the new locks. Is there anything else with the alarm system I should go ahead and replace or be aware of since I'm already doing all this?

Thanks guys.

 

Yes. You have two more in the front nose but than operate off the horn button in the column.

Horns were not installed at the back of the vehicle

Yes and pricey. If forum contributors don't post their favorites, I'll look them up in the NCRS Driveline and post

I have a 78 and have traced the horns/relays, etc and had the horns rebuilt...all three. I am attaching both the schematic and a description of how the anti-theft system works. Depending on whether your 78 is early or late, it could have the t-tops in the system as well. Sometime during Pace Car production (April) the tops were integrated into the anti-theft system.

I used Gary at the Horn Works who was also helpful with tips for checking the various components.

Horn Works

Schematic

Circuit Narrative

 

I know earlier Vette's had a horn behind the drivers side rear tire well. Mine has the holes but no horn. Probably just leftover from the earlier design and not used. But now I have to figure out what was cut off that wiring harness in the back. Hmm.

 

Power antenna?
What color wires? Green/gray/white?

 

Back horn for the ....back up alarm?

 

Hard to believe I've been working on this since March. LOL

Ok. Just an update. The holes behind the back tire WERE for the power antenna bracket which was removed along with the power antenna.

I gutted the whole interior. Replaced the front carpet, gauge panel, console panel (someone had painted them), new console side panels, new clock, new CD player, Hushmat and Reflectix on the floor, new AM/FM/CB power antenna and harness. Tons of stuff.

Anyways...my question...
I replaced the drivers side alarm harness/switch, the drivers side door lock tamper switch/pawl, the alarm relay, alarm flasher, and both T-Top sensors.

However, with the T-Tops out, when I arm the alarm, it doesn't sound. Everything else works fine now. Is this normal?

 

Ok I double checked everything today and still can't get it to work exactly right. I've replaced the T-Top switches, the relay, the flasher, and the door harness.

If I arm the alarm with the door open it will go off. If I arm the alarm with the door closed, nothing happens.

When I arm the alarm and open the hood or remove the T-Tops nothing happens.

If I have the door open and arm the alarm it goes off. If I then turn the key to un-arm the alarm it will turn off. However when I turn the key back to center to take it out I can hear the relay click again and it goes off again. This only happens sometimes. Its very temperamental.

If I arm it with the door closed and jiggle another key (ie the ignition key) in the lock it won't go off.

Any ideas how to troubleshoot it?

 

Here's a couple pics of the lock switch from the inside:

 

Sounds wierd...all the switches properly grounded? My 78 does not have the t-top switches so I have never played with that feature tho I do have a t-top alarm switch.

Well you know the alarm works, relay and flasher and some switches. I believe the door switches ground to the door while the switches have ground straps. Check those.

Arm the door with it closed. Leave the window open, pop the door **** from the inside than open the door. Than do it with hood and/or t-tops. I expect you'll get the same results.

I'm not sure "jiggling" is a test procedure in the ops manual!

If the relay is tempermental, it sounds like a loose connection. You should have consistency. Check all your wiring, grounds and connections.

 

sounds as if your t top and hood switches arent grounded.
http://www.corvetteforum.net/c3/tune.../index24.shtml

 

Ok guys. I'm still stumped. Using the diagram above I was able to trace the hood problem to a broken switch. One of the leads had broken off. Its replaced and works now.

I also got a ground kit from Zip Corvette and cleaned and changed the 2 frame grounds and one engine ground.

I connected a test light to the pos terminal on the battery and checked all the ground connections at the t-top switches and the anti-theft relay. They are all good now.

I still can't get the T-Top switches to work, even though they are new and the grounds are good.

Also, the switch in the lock is real touchy. If I arm the system with the drivers door open, it will go off. I then turn the key to the right to turn it off but as soon as I move it a little left it will go off again until I move it to top dead center.

How are the door ajar switches grounded? Each switch has a white and blue wire but only the blue wires are shown in the diagram above.

Also, any ideas how I can test the light blue connections at each switch in the diagram? If I arm the system, and put a test light from ground to them they should be hot right?

 

For some reason the T-Top switches started working. Not exactly sure why.

Now my final problem is the door lock.

If I arm the alarm by turning the lock to the left with the door open, the alarm will sound. If I then turn the key all the way to the right it will turn off. If I then turn the key just a hair to the left it will go off again until I get to 12:00 on the lock and then turn off.

I think I have a faulty switch. Anyone else have this problem?

Also, is my alarm horn supposed to sound this wimpy?

Here's a video of it.

 

I called Zip Corvette who I bought the switch from and sent them the video of me opening the t-tops and then operating the switch. They sent me another one free of charge to see if that was the problem. Awesome guys. I installed it. Same problem. It turns out it was an operator error. In order to get the alarm to turn off, you have to put the t-tops back in the locked position or close the door you opened to set it off. If you leave the t-top unlocked (or the door open) then it does what the video shows. Oh well. My bad.