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Pelican Technical Article:

Replacing the Horns

Mike Holloway

Time:

30 minutes30 mins

Tab:

$20 to $65

Talent:

*

Tools:

Phillips head screwdriver, 13mm socket wrench

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

Horn ? non OEM high pitch 400 Hz or OEM low pitch 335 Hz.

Hot Tip:

Remove any component to provide more room

Performance Gain:

A horn that sounds like it just rolled off the assembly line

Complementary Modification:

None

If most of your driving is done in the United States, blowing your horn at a fellow motorist is normally reserved for close calls or acts of severe displeasure. However, when driving in Europe or Asia, honking is almost required to allow other drivers know where you are in the space-time continuum. Therefore, the horn does provide an auditory signaling that is considered a safety device and should be kept in working order.

Like most cars, there are two horns on the Mercedes. This is done so that there is a harmonic pitch developed. As ironic as it may sound (no pun intended), a single horn would not be as pleasing to the ear.

The horn works by sending an electric current through an electro-magnet that causes a steel diaphragm to vibrate. This occurs when the diaphragm moves toward the electromagnet. When it reaches its apex, the current ceases and the diaphragm goes back to its original state. When this happens, the electro-magnet sends a charge again to bring the diaphragm closer. This cycle repeats and repeats and repeats until the circuit is broken by not pressing on the portion of the steering wheel designated for the horn to sound.

If your horn is not working at all, it is due to either a compromised circuit or a broken horn. The circuit may be compromised due to a blown fuse or corroded wiring. Both are easy to check. For the fuse, refer to the fuse box. The fuse box is located on the passenger side kick plate. Under the cover is a map to the various fuses. Locate the one designated for the horn. Replace if it is burned out. If it is not burned out, then it is possible that the connection is faulty or the horn has failed. Checking the connection will require a circuit tester (a small light attached to wire and alligator clips) or a multi-meter. You can use either one by hooking up the clips or leads to the horn leads and actuating the horn. You most likely won't be able to do this alone. Upon sounding the horn, if the circuit tester or multi-meter doesn't light up or the meter doesn't move then it is a wiring issue. Check every connection and make sure the wires were not cut. If the circuit is sound then the horn is compromised and has to be replaced.

Before you do any work on your car it is important that you wear safety glasses, work gloves and dispose of all fluids in a safe manner. Coolant is poisonous and should be treated as such. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. Always wear eye and hand protection and disconnect the battery.

The horn or horns may also have to be replaced if they sound exceptionally 'tinny' or are not nearly as loud as a horn should be. This could be due to internal corrosion or a compromised diaphragm. The horn is easily replaced by following the following steps.

Using a Phillips head screwdriver, loosen both leads that are connected to the horn.
Figure 1

Using a Phillips head screwdriver, loosen both leads that are connected to the horn.

Using a 13 mm socket wrench, loosen the remove the nut, which holds the horn in place.
Figure 2

Using a 13 mm socket wrench, loosen the remove the nut, which holds the horn in place.

The horn is now free to be disposed of and replaced.
Figure 3

The horn is now free to be disposed of and replaced. Installation is the opposite of removal.

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Comments and Suggestions:
Gil Comments: Since we're discussing the horns on a 380SL, how about some
guidance on removing the horn brush assembly installed at the top of the steering column. Anyone who has had to change out this brush unit please let us hear from you!!
04/28/2016
Gil Lusk
Knoxville, TN
April 27, 2016
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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