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1999 s420
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37 Posts
Discussion Starter #1
Hi guys, I have 1999 s420 the horn was working.just fine few days ago. And then I tried to use it yesterday it will not work. I looked up the fuses and fuse #25 in the engine compartment is blown. So I changed it to another 15A fuse. Horn wokrs...l Few minutes later, the horn stopped working. Checked the fuse again it was blown, I put anther after another new fuse and they are blown right away within seconds.... Everything else seems to be working fine only horn not working... And ideas or suggestions on what else to check ... Thanks for the help
 

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1992 600SEL and 1990 ford taurus GL
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270 Posts
you would have to do some searching on the horn wiring circuit for a short. long story short, from your description you probably have a short from a positive wire to ground. does it blow if you don't even use the horn? if the fuse blows even if you don't use the horn at all, then that means that the short is before the switch to activate the horn. if it blows only after you use the horn, then the short is after the switch. you could have a faulty relay as well. im not to sure where the relay for the horn is. you might want to do some searching on the forum.
 

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1999 s420
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37 Posts
Discussion Starter #3
Yes it blows without pressing the horn , as soon as I replace the fuse and turn the car on, the fuse blows.
 

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2003 S55 AMG Kompressor
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361 Posts
Adjustment of the airbag in steering wheel might be a poemtial cause if your horn is on constantly

you can try to replace the fuse by a light bulb (10w for example). if it's on, the horn would work. it saves you some fuses - and your neighbours won't blow a fuse while you are debugging this :)
 

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1992 600SEL and 1990 ford taurus GL
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270 Posts
Yeah this is more than likely a short to ground. I have taken a few auto electric classes, and have been over the exact same issue before.

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
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7,642 Posts
Check your hornpad wiring (behind the steering wheel airbag ) ,i had the same problem and by replacing those wires it stop't blowing the fuse .When the horn fuse blows you also dont have any blinker's , Right ? .:thumbsup:
 

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W140 Moderator
"CHRIS" Merc 92 600SEL / Sold > 93 600SE / 93 S500 / 89 560SEL / 413CDI / B180-CDI /A170-CDI
Joined
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7,642 Posts
No my blinkers are working just fine with the horn fuse being blown
Weird ,on mine they are all on that 1 fuse ,maybe they changed that as well on the later models .
Still check your hornpad wirings that nothing is touching and underneat the front bumper bars left & right edge corner were the actuall horns are (2 horns dont forget ) ,disconnect them ,check the wiring insulation then use some sort of spray like wd40 & reconnect ,could be a wire slightly cut on the upper edge between the bumper and chassis due to vibrations/movment etc from driving ,with a bit of luck you might get that to stop blowing the fuse ,i know how anoying that is . :thumbsup:
 
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