Horn constantly blows

[Taxbert]

The other night my 2004 Aveo's horn started blowing and won't stop. I unplugged the connector to the horn to make it stop. I thought it might be the relay so I unplugged the horn relay (under the floor mat next to the driver's left foot.). I reconnected the horn and it is still blowing. Still blowing without the relay!!! Any thoughts??? (When the horn was disconnected I would press the horn button and I can hear the relay clicking).

BTW, my alarm stopped working a couple of years ago. The doors still lock and unlock remotely, but it does not chirp when I lock it. Maybe related?

Thanks for any help.

[Taxbert]

Update. I unbolted the horn from the frame and plugged the the connector back in (with the horn relay also back in). Now when I press the horn button the horn honks without being bolted to the vehicle. I thought that bolting the horn grounds the horn. I am confused. Any Ideas. If there is a short, any ideas where the short might be or how to find it?

[petrified.rabbit]

check for power to the wire.. is there one or two? if the power is constant, it has a short to power. if there is only power when the you push the button then it might be ok.

not sure how you are testing it, but it "can" beep not bolted to the car, but not be properly grounded. so it would be muffled.

[Taxbert]

There are two wires going to the horn. I put a volt meter on the wires (negative to the battery, positive to the horn wire). One shows 12 volts, the other shows nothing, even when I press the horn button.

[petrified.rabbit]

ok. so it will beep since its a wire grounded horn.

the 12v should only have 12v when the horn button is pressed. if it is 12v when you pull the relay, that will tell you which side of the relay is short to power. the horn side.

might be in the fuse box, or harness.

[daug1502]

Aveo horn is 2 wire, one being the ground. I thought it grounded to body too, until I look at the actual wire, I believe orange for 12V Positive and Black for Ground Or Negative. I figure the colors should help you trace it out, good luck. the wire cover will pull back a little bit quite easily.

[petrified.rabbit]

thinking about this a little more.. it might have 12v constant, and a switch to ground to make it beep? (less power to the steering wheel, which is relayed anyhow but..)

so if the horn itself fails, and faults to ground it will be beeping forever..

put the test light in it, and hit the button, do it flash like it should or is it always on?

[daug1502]

Not very common to switch on the ground side of things. However I was taught to wire houses and cars tend to be backwards since they are Negative ground systems. Houses are Hot on the Negative side, Neutral on the Positive side, and if it's newer that third prong on there is your ground.

Back to the point, switching on the ground or neutral side of things can cause problems if a short happens due to the fact that there is a lot of wire that still has power available before the switch. Not to mention the Load (in this case the horn). You want to put a switch between the fuse and the load. I have the aveo manual on my computer, let me try to look it up.

CONTINUED

The horn switch is on the ground end of the system. When you press the switch it grounds the circuit and the horn goes off. I would start looking to see where there is a ground in the circuit, it's going to be between the horn and the switch.

[AveoJunk]

Not very common to switch on the ground side of things. However I was taught to wire houses and cars tend to be backwards since they are Negative ground systems. Houses are Hot on the Negative side, Neutral on the Positive side, and if it's newer that third prong on there is your ground.

You are comparing apples and oranges. Houses are alternating current and cars are direct current. In AC electron flow is in both directions, in DC electron flow is actually negative to positive. It is common to see the negative open. All of these devices are controlled through relays, so there is no direct horn to switch connection, switch activates a relay that supplies current.

[Ratchet104]

Most of GM cars are controlled on the ground side (AKA the switch is on the ground side)