horn goes off when i turn head lights on

hey guys i have an 2003 tacoma . i"ve been having an issue with my horn for the last week. when i turn my headlights on the horn randomly goes off. this is pretty shitty because now i can't dive at night. any help would be appreciated thanks

 

Do you have an aftermarket alarm system by chance? Just a thought, maybe the alarm box is having issues and triggering the horn.

 

Maybe try a new (or different-from auto wrecker) headlight switch.

 

The horn and HL switches are close together, and therefore the wires. Maybe the have been rubbing over the years, and are shorting to one another. You'll have to take apart the steering wheel to get to it, though. Long shot.

 

I'm having the same problem. What was the result of this issue?

 

do what tan4x4 said. it's not hard, just watch out for the air bag and keep track of the screws.

 

my first thought is before you go digging into the dash wiring, look at the wires under the hood for a short, trace them back from the horn and lights to where it goes into the firewall.

its a lot more likely that's where it will be if they are touching.

 

Sounds like a poor ground somewhere.

 

I don't think so. When the lights are on there's power. The horn randomly goes off when the lights have power. That tells me the 2 wires have been exposed and touching together. The column is easy to take the shrouds off and see what can be found. Then trace them from the column to where ever they go.

 

You'd be surprised at the crazy shit that poor grounds cause. Seemingly unrelated systems interact with each other in ways that only an exorcist could explain. Trust me.

 

I'm not saying they don't. I am saying start in at the column (end point) and work backwards checking the wires and grounds. It's a process of elimination that won't seem so overwhelming.

 

well while that is sound advice, the most common place for wires to be frayed, pinched, shorted, or damaged is under the hood which is why I prefer to tell people to start at the source and work your way back to the wiring harness and switches with the only exception is confirm the switch tests ok first.

 

My advice is to check all easily accessible grounds first. I've seen far more electrical problems result from poor grounds than I have two wires chafed and shorting to each other.

 

AGAIN, I am not arguing that. The point I am making, is that if a person has to ask, THAT person would more than likely be overwhelmed by popping the hood and going at it.

 

yet you recommended he start by pulling the air bag and going in to the dash wiring first?????

I wouldn't even suggest good mechanics do that unless they have some electrical training so they don't damage things pulling on wires, that's why I was confused by the suggestion to start by going into the dashboard without knowing if the guy has a clue about electricity or electrical troubleshooting.

even a noob can spot a pinched or skinned wire under the hood where its easy to access and see things but I wouldn't suggest anyone go anywhere near digging into the dash wiring unless they have the training to do it correctly.

 

A. The air bag is easy, 4 screws and a plug, to ensure it doesn't go off while working on it.
B. One doesn't have to take the the dash apart. Pulling the column shrouds and dash shrouds should give enough room to see under the dash to examine wires.
C. The best advice I can give someone who wants to try and work on their truck with out any "training" is, find a starting point, sack up, and do it. Otherwise, take it to a mechanic and pay through the nose.

 

I would first check the horn relay under the hood. They are cheap. There may be the same relay in another slot that matches the horn relay. Swap them out and see what happens.

 

I understand your recommendation better now

 

Did you get it fixed