Does your horn work without the keys?

renaud33

New member
stupid question but my aftermarket horn in my 2016 only works with the ignition on or running. can't remember if the stock worked without the key...
 

220629

Well-known member
To my knowledge the OEM Sprinter steering wheel horn switch/relay only works when the ignition key is on.

vic
 

crowdedvan

New member
I learned this the hard way. I was sitting in my stock 2016 in a parking spot (no keys in the ignition) when a car in front of me was backing out of a spot. She was getting closer and closer to the point I felt like I needed to honk to let her know to stop. To my surprise...no sound at all. She ended up bumping me. Afterward I put the key in the ignition and then the horn worked. Ugh.
 

220629

Well-known member
I don't understand the logic of not having a horn at all times. As you point out, there are key off times when it is needed. It is a common design in German vehicles.

vic
 

jzf0fk

Member
Is there a way we can rewire the horn so that it works without the key in the ignition? Is there a risk of draining the battery?
 

220629

Well-known member
Is there a way we can rewire the horn so that it works without the key in the ignition? Is there a risk of draining the battery?
Electrically it shouldn't be a big issue.

My memory is that the steering wheel horn button(s) operate the horn relay by switching to ground. That should mean that a constant 12 volts could be used to feed the relay in place of the OEM key on source.

Depending upon the relay location and harness routing, accessing the wiring to interrupt/replace the OEM power source could be a bit of a challenge. If lucky, it could be simple.

Feeding constant power to a relay that is switched to ground will not drain the battery. That is the method used for most Detroit iron vehicle horn relays.

vic
 

crowdedvan

New member
This is slightly off topic, but relevant. The incident I described above happened about 5 months ago. The car left a slight scratch on the plastic bumper, so we just let it go. Now fast forward to this past weekend, the collision avoidance system now says it's inoperational. I took it to the dealer figuring it would be covered under warranty. They just told me because they see a scratch above the sensor on the bumper they have to treat it as damage repair and not warranty. I now have to pay just for them to inspect the bumper to see if the sensor will be covered under warranty. This horn feature just cost me $260 just for the inspection. I'm so mad right now.

-Tim
 

220629

Well-known member
A relatively cheap solution for a horn that works all the time.

Harbor Freight has some cheap, but effective dual horns.

https://www.harborfreight.com/2-piece-12-volt-electric-horn-set-99911.html

I put a set on my wife's 1995 Buick. They sound like, and the loudness is similar to traditional Detroit car horns. The included relay can used with fused power directly from the battery to wire the horn to work with key off. The OEM horn would be disconnected. The negative switched OEM wire will need to be tapped for one side of the horn relay coil.

vic
vic
 

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