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1999 ML430
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53 Posts
Discussion Starter #1
Hey All,

I am not sure if there is a connection or not, but I was messing around with my fuses and I inadvertenly dropped the horn relay switch. I put it back in, but now my horn doesnt work. Is there some type of resetting process that needs to be done, or could I have broke the relay? Also, I checked the fuse and it was okay.

Any help would be appreciated! Thank you...
 

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Premium Member
02 ML320 06 ML500
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17,098 Posts
Wouldn't it make sense to swap the horn relay with a similar one in the fuse box; in that way you will find out if the relay was damaged.
 

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1999 ML430
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53 Posts
Discussion Starter #3
43...

I did switch the fuel pump relay with the horn relay and the horn still DID NOT work. I could however here a clicking noice in the relay when I pressed the horn. Do you think I need a new horn?

Thank you...
 

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Premium Member
02 ML320 06 ML500
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17,098 Posts
43...

I did switch the fuel pump relay with the horn relay and the horn still DID NOT work. I could however here a clicking noice in the relay when I pressed the horn. Do you think I need a new horn?

Thank you...
You should have provided this info. in your first post and things would have been easier.

Then go to both horns, one on each side under the bumper. Remove the connectors, and clean each prong on the horn with sand paper or a wire brush and you will be good to go.
 

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1999 ML430
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53 Posts
Discussion Starter #5
Sorry 'bout that 43...I will try to be more thorough.

So here is where I am at!

Unbeknownst to me, I have THREE horns. There are two mounted under the front bumper, and one mounted on the firewall on the drivers side. I checked the two under the bumper and one only had one of the wires hooked up (the other wire broke off at the post), the second under the bumper horn was very corroded. I took all three horns off and attached to the battery on my cordless drill...only one horn works and thats the one mounted on the firewall. There is no corrosion on this horn or the connections...but when I hooked it back up, it wouldnt work.

any suggestions?

Thank you for your time...
 

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02 ML320 06 ML500
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OP, the one on the firewall is your alarm horn. Just return it to its' proper place.
 

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ML430 '99' E280 '94'
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17 Posts
Simply replace the two horns in the bumper with new ones - one is a high and one is low tone.

They are easily available from any car spares store, after fitting you can apply some water resistant battery grease or silicone sealant around joints to prevent future failure.
 

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Currently owner of 2 x ML 320 - 2000 & 2001/Sport
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56 Posts
I too have a horn problem, my horn does not work, I'm suspecting bad horn switch, could anyone share the schematic & instructions as to how to get to the switch safely, without exploding the airbag? I know it's in the steering wheel; how to get it apart?
 

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02 ML320 06 ML500
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I too have a horn problem, my horn does not work, I'm suspecting bad horn switch, could anyone share the schematic & instructions as to how to get to the switch safely, without exploding the airbag? I know it's in the steering wheel; how to get it apart?
Extremely rare that the horn switch/contact is bad. First check fuse #37; if not, remove the horn relay K2, in the underhood fuse box. With the key on, jumper the two slots in the fuse box with a short piece of wire that were occupied by the two prongs in the photo.

If the horn does not sound, then remove the connectors on both horns and clean connectors and horn prongs.

If the horn sounds, then switch the relay with similar and test again.
 

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Currently owner of 2 x ML 320 - 2000 & 2001/Sport
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Hi 43 sqd, I did exactly as prescribed, no luck, it's cold so I have not checked the connectors on the horns yet, will do that hopefully this week, wanted just in case to know if I can take get to the HORN SWITCH myself,
will let you know when I inspect the horns
 

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1998 ML320, 2005 C240
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45 Posts
Simply replace the two horns in the bumper with new ones - one is a high and one is low tone.

They are easily available from any car spares store, after fitting you can apply some water resistant battery grease or silicone sealant around joints to prevent future failure.
If removing the old horns yourself, be careful!! Often times the bolt and nut holding the old horns on are so corroded, the bolt can actually break off, leaving you finding another place to mount the horn, or having to drill out the old screw. Make sure you use some WD-40 to loosen everything up. Installation is pretty simple. Good luck!
 

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Hi 43 sqd, I did exactly as prescribed, no luck, it's cold so I have not checked the connectors on the horns yet, will do that hopefully this week, wanted just in case to know if I can take get to the HORN SWITCH myself,
will let you know when I inspect the horns
If you are absolutely sure that your jumper wire made contact and fuse #37 is not blown and the key was on, then your problem cannot be the horn switch. By jumping the relay you eliminate the air bag and horn switch.
 

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If removing the old horns yourself, be careful!! Often times the bolt and nut holding the old horns on are so corroded, the bolt can actually break off, leaving you finding another place to mount the horn, or having to drill out the old screw. Make sure you use some WD-40 to loosen everything up. Installation is pretty simple. Good luck!
WD-40 police will have chat with you.:rolleyes:
 

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Currently owner of 2 x ML 320 - 2000 & 2001/Sport
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Hello 43SQD!, my congratulations, again, fixed the horn, it was/were the horns that have gone kaput!, replaced both and all is OK again, thanx
 

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2000 ML430 (Sold)
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Sorry to bring this up, just wanted confirmation. My horn went out two days ago and couldn't figure out why. I tested for voltage with the steering wheel horn "button" pressed, got nothing.
Did the test as 43sqd said above and got the horns to blast with a wire between the terminals. Im assuming this means there's a problem between the fuse-box and the contacts in the steering wheel, most likely being the contacts themselves are messed up.
Just wanting confirmation before i take the wheel apart tomorrow.
BTW, the key does NOT have to be turned on to supply voltage to the fusebox. Scared the shit outta me when my supertones blasted and i didnt have the key in.
 

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Sorry to bring this up, just wanted confirmation. My horn went out two days ago and couldn't figure out why. I tested for voltage with the steering wheel horn "button" pressed, got nothing.
Did the test as 43sqd said above and got the horns to blast with a wire between the terminals. Im assuming this means there's a problem between the fuse-box and the contacts in the steering wheel, most likely being the contacts themselves are messed up.
Just wanting confirmation before i take the wheel apart tomorrow.
BTW, the key does NOT have to be turned on to supply voltage to the fusebox. Scared the shit outta me when my supertones blasted and i didnt have the key in.
Did you substitute the Horn Relay with a similar one in the fuse box and did you check the fuse?
 

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2000 ML430 (Sold)
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Yes to both. Fuse has been upgraded to a 30A which was not blown and relay has been changed to the one supplied with the Hella Supertones. Even with a known good OEM relay in the spot though i get nothing. Neither relay will click.
 

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02 ML320 06 ML500
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Yes to both. Fuse has been upgraded to a 30A which was not blown and relay has been changed to the one supplied with the Hella Supertones. Even with a known good OEM relay in the spot though i get nothing. Neither relay will click.
Installing a higher amperage fuse is bad for wiring. The horns only require a 20 amp fuse.

Remove Horn Relay K2 and fashion a 4" jumper wire with spade terminals attached, the same width as the thinner pins on the relay.

Insert one end of the jumper wire into slot 30 in the fuse box and test for B+ at the other end, then remove and do the same for slot 86. You should have B+ at both 30 and 86. If you don't then there is a problem in the fuse box.

If you get B+ at both, then insert one end of the jumper wire into slot 85, and while someone presses the horn pad you test for a ground signal at the other end of the wire.

Please note that a spaded jumper wire must be used because each relay slot has one contact point.
 

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