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Horn Keeps Going Off When Trying To Hook Battery Back Up

jdewolfe

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jdewolfe Enthusiast

jdewolfe

Posted
Posted

Hey guys- I was just out of the country for about 2 weeks. While out, I had the battery in my truck un-hooked so that I could reset the computer. Never done it since I owned it and I figured it wouldn't hurt anything. I went to hook it up this morning and as soon as I touch the negative cable to the battery, the horn starts going off like the theft thing is activated. How can I avoid this from happening? It's very loud because the truck is sitting in underground parking and I don't want to bother the neighbors. Maybe leave the key in the ignition while doing it? Just looking for some ideas.

 

Thanks for the help!

Jeff

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

Nothing in the factory content theft system should be causing this. The only time that I've ever had this happen to me was on a vehicle with an aftermarket alarm system installed.

GasHog369 Senior Enthusiast

GasHog369

Posted
Posted

How bout popping out the fuse for the horn?

 

:)

 

 

also. are both cables unhooked? If so u always want to hook up the positive first , and or disconnect negative first.

 

This way the computer wont be trying to power off the negative current.

RockySierra Enthusiast

RockySierra

Posted
Posted

Have you tried hooking the cables up, then trying to stop the horn with the panic button on your FOB or putting the key into the ignition? Are your doors shut when you hook up the battery?

old-chevy-dude Senior Enthusiast

old-chevy-dude

Posted
Posted

my horn goes off when ever I disco and reco the battery on my 2010, my Chrysler did it, my Impala did it, my Caddy does it, IF the any of the doors are open when you reco the battery..

 

 

pretty common as I have seen for any alarm system, OEM or otherwise.

 

 

connect the battery and press the unlock on your fob.. if you don't have a fob, then remove the horn fuse or relay as suggested..

redsled2007 Enthusiast

redsled2007

Posted
Posted

I just turn the key to "ON" before I hook the battery up. It disables the alarm. The alarm is from your hood being open.

Wires Enthusiast

Wires

Posted
Posted

My 2008 does this if the battery was disconnected, and it was locked with the fob (aka in "theft mode").

 

Perfectly normal. Stuff cotton in your ears, connect the negative terminal, and hit the unlock button on the fob. :rolleyes:

jdewolfe Enthusiast

jdewolfe

Posted
  • Author
Posted

I put the key in and turned it to on. It only beeped once and then was good. Thanks guys!! :-)

ChevyTech77 Senior Enthusiast

ChevyTech77

Posted
Posted

I went out, after work last night, and tried this on my neighbor's '05 and my '11 and NEITHER of them set the ctd alarm off when reconnecting the battery cables. Both trucks were locked with the key fob putting them both into active ctd status. Must be a different combination you guys are using and yes, I found this interesting enough to try for myself. Gave me a chance to drink a beer with the neighbor anyway. :rolleyes:

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted
also. are both cables unhooked? If so u always want to hook up the positive first , and or disconnect negative first.

This way the computer wont be trying to power off the negative current.

 

The reason you disconnect negative first and connect it last is simply so you can't short the positive cable to ground with your wrench accidentally. Nothing at all to do with the computer. All electrical devices need a complete (otherwise known as a closed circuit) circuit to operate. Disconnecting either of the battery cables opens the circuit.

Wires Enthusiast

Wires

Posted
Posted
I went out, after work last night, and tried this on my neighbor's '05 and my '11 and NEITHER of them set the ctd alarm off when reconnecting the battery cables. Both trucks were locked with the key fob putting them both into active ctd status. Must be a different combination you guys are using and yes, I found this interesting enough to try for myself. Gave me a chance to drink a beer with the neighbor anyway. :rolleyes:

 

Odd. I wonder if there is a difference between the Sierra and Silverado?

jdewolfe Enthusiast

jdewolfe

Posted
  • Author
Posted

I have a feeling it was going off because when I unhooked the battery I had all doors locked. Of course I had to pop the hood to hook the battery back up, so I had to unlock the door with the key and I wonder if it noticed that when hooking the battery up? Anyways, leaving the key in took care of it. Thanks again!

  • 9 months later...
agonzal4@aol.com New Member

[email protected]

Posted
Posted

I've had the same problem yesterday. I was eating a sandwich with the truck running and all of a sudden my horn goes off big time. I turned the vehicle off, the horn stopped for a second and than went off again. I finally had to open the hood, and undo the positive cable connection. I than took fuse #30 out and when I hooked up again, no horn (of course).

I decided to come on home and on the way my cruise control did not work, so I just kept on coming home. About half way and approximately every three miles, my on-star came on momentarily, with "please hang up and call again" through the speakers and did this about 4 times. At the end, it always thanked me. I have an appointment tomorrow morning with Allen Samuels Chevrolet in Corpus Christi, I shall come back and give you the results. I have a 2007 Chevrolet Silverado, Texas Edition with 68,000 miles. I also have an extended warranty hope that helps, for sure(?).

MikeNH Senior Enthusiast

MikeNH

Posted
Posted
I went out, after work last night, and tried this on my neighbor's '05 and my '11 and NEITHER of them set the ctd alarm off when reconnecting the battery cables. Both trucks were locked with the key fob putting them both into active ctd status. Must be a different combination you guys are using and yes, I found this interesting enough to try for myself. Gave me a chance to drink a beer with the neighbor anyway. :rolleyes:

 

Odd. I wonder if there is a difference between the Sierra and Silverado?

 

No difference.

 

 

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