gsimon767

I replaced the alarm switch inside the fender and replaced door switches. I made sure the switch button was depressed against the lever turned by the key as specified in the AIM manual. Now the alarm horn sounds when I turn the key to arm the system. The door switches appear to be adjusted correctly as the door ajar light functions as it should. I think the hood switch is adjusted correctly. What would make the alarm sound when I turn the key to arm it?

In general can anyone explain how the system is supposed to work.

Peterbuilt

Have you checked the relay?
Could it be that the contacts are stuck closed?

Or has the flasher gone bad?

righthanddrive

You could also eliminate one switch at a time by unplugging the wires to it, thereby assuring the contacts are open.

My guess is the fender contact is the culprit

gsimon767

i don't think it has anything to do with the relay or flasher as it honks the horn repeatedly. I have checked that the door and hood switches are depressed when the key is turned to set alarm. Turning the Key on the fender switch causes the horn to activate.

How do I check the fender switch to see if it is defective or not adjusted properly. I don't understand how turning the key to set the alarm causes it to honk and when I turn the key to off the horn stops honking.

I suspect the new fender switch but it is so hard to get to I don't want to try to readjust or replace it unless I have to.

righthanddrive

If you look at the exploded diagram above, it shows a tab " B" that should depress the button "A " when armed.

Check and make sure the " 1 " is forward enough to depress " A ". If it is, then one of your contacts ( door or hood ) is setting the alarm off.

'75

This is from a 77, but should have all the same switches. Left side of the page.

OLE442

gsimon767......just curious how this was resolved. I have the same issue with my low mile 1976 C3. It was re-painted 3 years ago so I'm wondering if a wire were left off or something was not put back correctly. When I turn the key/switch on the fender, the horn sounds within a second or so? It was my deceased cousin's car so I can't ask him about previous issues. He owned it for 25 plus years.

DUB

YES...that fender switch is a royal PAIN to get to and adjust. Unless the car is being judged...I let my customer know that this alarm system is so outdated and actually nothing but a noise maker and drains the battery....it is best to leave it inoperative. Some of them still pay me a lot to get it working....and usually costs more than a more current system that can be installed...or at least upgrade it to the theft system GM used later on....which has a starter interrupt and shuts down to save battery live.

I bet your under hood switch is the problem. Those are very touchy and can fail.

DUB

gsimon767

Dub is correct. The fender anti tamper switch was my problem. You can see the switch in the AIM manual if you have one. The switch has a button on the side that presses against the back of the keyed fender switch. If the anti tamper switch button is not pushed in against the back of the fender switch the alarm will activate when the key is turned to set the alarms, assuming the rest of the system is working. Over time the plastic anti tamper switch can crack enough that the button is not pushed tightly against the back of the switch causing the alarm to sound.

It seems that if a thief punches out the keyed switch they will cause the button on the anti tamper switch to release and sound the alarm. Crude but effective.

There are two wires to the anti tamper switch. I assume it can be bypassed if the two wires are connected. I ordered a new switch and made sure the button was pressed in tIghtly. It is very difficult to get to but can be done by reaching under and arround the master cylinder to loosen the nut under the switch.

lvmyvt76

how about the switch under the hood, that goes off if the hood is raised?? (my 76 has it , don't know what year yours is.) Make sure you have the correct switches, also.

OLE442

Does anyone know if parts 2,3 and 4 from the diagram in the above post are available out there in Corvette land?

gsimon767

It sounds like even though you think the button on the fender switch is pushed in, it is not. I had to wedge a large socket between the edge of the mounting shelf and the switch while I tightened the nut on the bottom of the switch. The socket kept the button depressed while tightening the nut. I had the exact same problem you are having. You can take the switch out of the circuit by unplugging the switch wires. If you can then turn the key without the alarm sounding the switch button is not depressed enough. It takes a lot of pressure to hold the button in.