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Replacing a car horn switch
August 9, 2010 7:36 PM   Subscribe

Help me replace, rewire, or otherwise rig the horn switch in a Dodge steering wheel.

I am attempting to replace the horn pad in a Dodge Neon. The thing went wonky and started blaring on its own (some kind of short, I figure). I started out trying to find the actual part, of course, but after what I deem to be enough frustration on that front, I'd like to replace it with something else, in any way that works. (Also, this is my idea of fun.)

The horn pad is apparently a membrane switch. It fits in the narrow space under the soft plastic steering wheel casing, on top of the hard plastic casing on the airbag assembly. There are a few extra millimeters of space under the decorative Dodge symbol button (button probably can be removed).

How can I make it work? Looks don't matter much-- it could end up being a big green AskMe button for all I care. On the other hand, cost is an important factor.
posted by zennie to Grab Bag (9 answers total)
 
I would suggest coming up with a design that does not involve the steering wheel casing, because when the airbag goes off, a part added by a DIY modification might be converted into a bullet into your face.

I guess I'd cut the wires and remove the membrane pad on the assumption that the false connection is coming from the pad. (If the problem persists after doing this, sheepishly reconnect the membrane and start looking for rodent chew marks in your wiring harnesses :)

Then extend the wires and replace with any old switch, preferrable something big and cool and red, which you mount on the rim of the wheel (ie well clear of the path of the airbag), possibly like it's the fire control on your James-Bond-car missle launchers :)

Be careful doing anything near the airbag assembly.
posted by -harlequin- at 8:43 PM on August 9, 2010


If you can find a wiring diagram, you can figure out which wire going in to the steering column is the horn wire. From there you could install any sort of pushbutton switch on your dash - the horn wire just has to make contact with the vehicle ground to work. (this is probably the most airbag safe option)
posted by davey_darling at 10:09 PM on August 9, 2010


I'm a big DIYer, but if you're having trouble with this at all, consider taking it to someone. Remember, airbags don't gently inflate, they explode. Whatever you're using to pry off bits of steering wheel will suddenly become projectiles. Airbags aren't something to mess around with, really.
posted by InsanePenguin at 3:14 AM on August 10, 2010


Before you start working on the steering wheel, it's critical that you disconnect the battery and wait a few minutes. Most airbag control modules have a little back up capacitor in them to ensure there's power to trigger the igniters. So let the capacitors discharge before taking the steering wheel apart.
Most car horn pads and buttons work by grounding the signal side of the horn relay. So while replacing the horn pad, it's really easy to put it back together a little wonky and ground the horn relay by accident. Instead of tearing the whole thing apart, you should start by fixing what you worked on. Remove the horn pad and see if it shuts up. Then carefully examine the switch contacts as well as the rest of the area. ANY part of the metal horn pad frame that contacts the bare metal of the steering column will complete the ground circuit. The most likely scenario is that the horn pad went back in wrong and is grounding out. You probably don't need to rewire anything. This has happened to me once or twice and you probably just need to adjust the horn pad. I've also seen horn pad springs wear out and allow the pad to contact constantly.
posted by Jon-o at 4:17 AM on August 10, 2010


Err, I misread your original post. I thought you already replaced the horn pad and now it's sounding all the time. If it just started happening, don't just assume it's the horn pad and start some big project. The horn relay could be getting it's ground from another source and you don't want to do all this work only to not fix the problem, right?
What I would do first is swap the horn relay with another identical relay (washer pump, high beams, whatever fits) and rule out the possibility of the relay being stuck on. If it doesnt stop, then remove the horn pad. If it's quiet with the horn removed, it's possible that you can compensate for worn horn springs or a worn switch.
posted by Jon-o at 4:30 AM on August 10, 2010


I would suggest coming up with a design that does not involve the steering wheel casing, because when the airbag goes off, a part added by a DIY modification might be converted into a bullet into your face.

Good point.


Airbags aren't something to mess around with, really.

I'm not touching the airbag, it's disconnected, and it's electrically separate from the horn. I disassembled the steering wheel according to procedure. Once you get the bolts out, it just falls open.


What I would do first is swap the horn relay with another identical relay (washer pump, high beams, whatever fits) and rule out the possibility of the relay being stuck on.

Yeah, I checked that.

I was a little thrown by the fact that there are no springs and nothing overtly mechanical, like a switch to check. Just that thing! Got any ideas? Just a switch on the outside? Maybe I could mount something on the dash.
posted by zennie at 6:48 AM on August 10, 2010


I was a little thrown by the fact that there are no springs and nothing overtly mechanical, like a switch to check. Just that thing!

That thing actually is a switch. It is two conductive pads that are separated by hundreds of very tiny plastic bumps that keep them separated by a few micro-inches. When you press on it, you deform the upper pad between the bumps so they make electrical contact just like a switch.

So you can test the pad just like you would test a switch. With an ohm meter you should have infinite resistance between the two electrical leads normally, and a few ohms when you press your finger on the pad.
posted by JackFlash at 8:48 AM on August 10, 2010


Yes, but the problem is the switch is never "off", so the horn blares. I haven't checked it with a meter, but from the wear and dents and separated plastic on the membrane switch, among other evidence, I'm pretty certain about that.
posted by zennie at 9:12 AM on August 11, 2010


You could try and find a replacement switch from a similar car at a junkyard, or suck it up and buy one from a dealer.
posted by exogenous at 8:17 PM on August 14, 2010


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