77Dream

OK, on my 77 I have the stock alarm. The alarm switch is in the drivers door lock. My problem is every time I try to set the alarm it just goes off. Does anyone know what the problem may be? If I want to lock the door I have to lock it from the inside before I close it.

77Dream

Anybody? :confused: I'm not good with electrical stuff and this sounds like it might be a wiring problem.

bence13_33

The same thing happened to my '76's alarm system. There is a mercury sensor for the car alarm. If anyone ever tries to towe away your car, once it reaches a certain angle the mercury sets off the car alarm. It sounds like this might be bad...it was with mine. I disconnected the mercury sensor and mine works fine. The sensor is located right below the windshield washer fluid reservior. Try this and see what happens.

77Dream

That sounds like it might be the problem, but I looked under my windshield washer fluid reservior and all I seen was my carbon canister (I think). Nothing that looks like it might be the mercury sensor. Would it be in a different place on a 77?

Thanks.

bence13_33

The sensor should be mounted to a piece of fiberglass and should have two wires going to it.

jetech

Here are some things to look at

The ANTI THEFT PROTECTOR SWITCH which is part of the ANTI THEFT CONTROL SWITCH located in the LH door lock. The anti theft horm will sound any time the anti theft protector is closed regardless of whether the alarm has been set or not.

The LH and RH DOOR SWITCHES, they are normally open with the doors closed. Also the ANTI THEFT HOOD SWITCH which is open with the hood closed. These three switches are hooked together. If any one or more of these switches has failed to ground (simulating an open hood or door) the alarm will sound.

One or more of these components will most likely be the problem. Make sure the doors and hood are closed before setting the alarm. My fender mounted control switch was corroded and wouln't turn, the door mounted switch may be better protected from the elements but can probably still get wet. Try removing each switch one at a time from the circuit to isolate the faulty switch.

Hope this helps :cheers:

BSeery

Mine did the same thing on my 1980. I checked all the known switches and still had the problem.

On mine, the t-tops had switches in the mounting holes where the locking rods went into the body near the side windows. Inside those holes are a switch for the alarm. The rods on my t-tops were not extending far enough into the holes to turn the switches off.

I don't know if those switches are on the 1977 and earlier models.

jetech

The wire schematic doesn't show any t-top switches for the 77. If all the switches check out start lookng at the rest of the system. If all components are good then it is time to start checking wire runs for a short to ground. Just dont give up :smash: :cheers:

gliot1

The stock system has no mercury switch. I just troubleshot my '78; the full cicurit schematic is available in GM manuals. If you set the switch and it immediately goes off, you probably have a bad switch. There are (3) switches all wired in series; any one fails the alarm goes off. The switches are at the doors and the hood. Be aware that there is a protective switch of some sorts, which cause an alarm trigger if the lock is tampered with or drilled; it too will set it off. The switches are normally open, meaning when a door or hood opens it shorts. You can check these with an ohm meter, or try jumpering every switch. If you door lights work propely when the doors are opened or closed, I would first check the hood switch. The alarm is activiated by a relay under the console, this could also be a cuplrit. With all doors and hood closed you should be able to turn the key to the left and hear no "click" of the relay. I suscpect it will click, as the alarm is activatiing. There is a flasher in the circuit as well, which pulses the alarm. If your alarm pulses the flasher is probably good. the flasher and relay are right below the heater control. This is very fresh in my head as I just fixed mine (2) weeks ago and worked thorough the entire circuit. The only difference is that mine wouldn't alarm; I had a bad flasher. The schematic is posted on a couple of web sites, though I don't have them bookmarked. Search a little you will find them; even in color. An volt/ohm meter is helpful, as well as a 12V test light. Good luck!!!! :smash: :mad :smash: :mad :cry :smash: :)

gliot1

One more thing.......the T-top switches wern't added until very late '78. I have an early '78 and there are no switches. You're '77 should have no switches there; if you did they would be part of the grommet where the back rod inserts into. :chevy