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High and Low Tone Horns Replacement
 
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Pelican Technical Article:

High and Low Tone Horns Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$40

Talent:

**

Tools:

10mm, 13mm socket, trim panel tool, DVOM, test light

Applicable Models:

BMW Z4 Convertible (2003-08)
BMW Z4 Coupe (2006-08)

Parts Required:

high and low tone horns

Hot Tip:

Be sure to properly position horns to prevent water intrusion

Performance Gain:

Working horns

Complementary Modification:

Replace horns in pairs

BMW Z4 models are equipped with two horns, a high and low tone. A vehicle horn is a sound-making device used to warn others of the approach of the vehicle or of the vehicle's presence.

BMW Z4 model horns are electric, driven by a flat circular steel diaphragm that has an electromagnet acting upon it and is attached to a contactor that repeatedly interrupts the current to the electromagnet. This arrangement works like a buzzer; with sound levels around 107-109 decibels and current draw 5-6 amperes. BMW Z4 model horns are arranged in pairs, sounded together to produce two notes. The paired horns only increase the decibel output a small amount, but the two different notes are more perceptible, especially in an environment with a high ambient noise level.

The horn circuit on Z4 models is not complicated compared to other models of the same vintage. The horn button in the steering wheel is activated by the driver. That request for the horn is sent to the power distribution panel; activating the horn relay which in turn activates the horns. For more specific info, see the end of the article for an overview of how to test the horns.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If 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.

Our vehicle may vary slightly from yours as models do change and evolve as they grow older. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please include your vehicle information.

There is a high tone horn mounted in the right side of the bumper cover (red arrow) and a low tone horn mounted behind the left side of the bumper cover (blue arrow).
Figure 1

There is a high tone horn mounted in the right side of the bumper cover (red arrow) and a low tone horn mounted behind the left side of the bumper cover (blue arrow). Replacing either horn is similar. I will show you how to replace the low tone specifically. Start by removing the left front wheel well liner. See our tech article on wheel well liner replacing.

With the wheel well liner removed, you have clear access to the horn (red arrow).
Figure 2

With the wheel well liner removed, you have clear access to the horn (red arrow).

Start by disconnecting the electrical connector (red arrow).
Figure 3

Start by disconnecting the electrical connector (red arrow). Press the release tan and pull the electrical connector straight off the horn.

Note the orientation of the horn.
Figure 4

Note the orientation of the horn. Then remove the 10mm horn fastener (red arrow). Once the fastener is removed, remove the horn from the vehicle.

If you need to replace the horn mounting bracket (blue arrow), remove the 13mm fastener (red arrow), then remove and replace the bracket.
Figure 5

If you need to replace the horn mounting bracket (blue arrow), remove the 13mm fastener (red arrow), then remove and replace the bracket.

The horn should be marked to identify the tone (red arrow).
Figure 6

The horn should be marked to identify the tone (red arrow). Always double check when replacing as the horns may have been switched at some point. Reverse steps to install new horn.

Horn testing: To test a horn, start by checking the horn fuses located in the interior fuse panel.
Figure 7

Horn testing: To test a horn, start by checking the horn fuses located in the interior fuse panel. For my vehicle, fuses 14 (blue arrow) and 37 (red arrow) are for the horn relay. Check that both of those fuses are OK. If both fuses are OK, check the signal into the fuse panel from the horn buttons. For my vehicle, terminal 6 on connector X11008 should be the horn button lead. It should have battery volts when the horn button is off, when the horn button is on, it should be close to zero volts (ground). The horn switch grounds this wire. The relay should send battery volts to the right (high) horn on terminal 3 and the left (low) horn on terminal 12.

Horn testing: Access the horn that is not working.
Figure 8

Horn testing: Access the horn that is not working. Then, disconnect the electrical connectors. Connect a DVOM across the horn terminals. These are the two horn terminals on my subject vehicle, red arrow points to battery positive feed to the horn, blue arrow points to the battery negative feed to the horn. Turn the key ON, press horn button. When the horn button is pressed, you should have battery volts at the terminals, (about 12 volts). I suggest load testing using a test light and a DVOM. Connect DVOM across the horn electrical connector terminals and take a reading, it should read battery volts when the horn button is pressed. Then connect an incandescent bulb style test light to battery ground and touch the test light probe tip the positive wire you are backprobing with DVOM. Your reading should hold steady, a maximum drop in voltage of 0.5 volts is OK. Anything more is a problem. If you have no voltage to the horn, the problem could be with the wiring from the fuse panel to the horns or a faulty ground.

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Page last updated: Sat 12/3/2016 03:07:44 AM