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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3722
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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E550: Marty, i have a 2007 W211 E55, the horn has stopped

Customer Question

Hi Marty, i have a 2007 W211 E55, the horn has stopped working and i have
*Checked and replaced all associated fuses
*Run test on relay (working)
*Have continuity at horn and horn connections
*With ignition on and horn pressed the multimeter does not spike to 12 volt..
Should i begin the process of removing the horn from the steering wheel?
Please help!!
Submitted: 1 year ago.
Category: Mercedes
Expert:  Lou P. master tech replied 1 year ago.
Hello my name is ***** ***** i will do my best to help you , i strive for EXCELLENT service and nothing less. I will check a diagram in the morning and help you come to a conclusion. I believe you need to remove the airbag to check and make sure the wire did not come loose. But hang tight.i will provide you with the diagram so we can be on the same page. Lou
Customer: replied 1 year ago.
Hi Lou thanks for that i will wait for your reply. Aaron
Customer: replied 1 year ago.
Hi lou I have since removed the Airbag and checked and tested the wiring and contacts but with no luck... any help would be appreciated.. also have run full diagnostic and no fault codes.
Expert:  Lou P. master tech replied 1 year ago.
Ok , I'll have the info for you soon. I'm just getting up and going here.
Customer: replied 1 year ago.
Ok still waiting lol
Expert:  Lou P. master tech replied 1 year ago.
Just realized your time zone. I am in USA. It's 6am here. My apologies. I'll be back in a hour as the info is only available on site at work.
Customer: replied 1 year ago.
No worries mate
Expert:  Lou P. master tech replied 1 year ago.
Ok , appreciate it.
Expert:  Lou P. master tech replied 1 year ago.
checking now
Expert:  Lou P. master tech replied 1 year ago.
http://www.mediafire.com/view/2vct5m133264f69/211_sam_fuse_box_left.jpg
copy and paste that link, check the position of fuse , make sure it is in the 'A" position. in the 'A' position the fuse will have power with the key on, in the 'B' position the fuse will have power all the time. if the fuse is correct and good. and you can apply power to the horns and activate them yourself, and have swapped the relay to test with another relay, then you have 1 of 2 issues, the control module inside the column is not sending the horn signal by communication wires, or the front left SAM (that is what the fuse box is called , it is actually also a control module) is not seeing the signal and not activating the horn. the horn system is not a simple on off wire and relay. so if you came into the shop, the way we would test it is to hook up the scanner and use the scanner see if the control module recognizes the horn being pressed, if it does not then the column module is bad, if it does see the signal then we would use the scanner to activate the horn. and while it is activating we would check for power at the horn. if the scanner says it is activated and there is no power and the fuse and relay are good and the wiring is good then we would say the module is bad. so i think you have done all you could. you need a scanner to determine if the module sees the signal when pressing the horn. so to recap, when you press the horn, a switch is grounded inside the steering wheel control buttons ( that reminds me, do the steering wheel buttons work??) and then the signal is transmitted over the communication lines to the front left sam ( fuse and relay box) and then the sam internally activates the relay ( relay position O) and then if the fuse is good (53a) then the power is sent to the front horns via the yellow wire. and also the ground for the horns is just behind the front headlight ( on the right side of the car if looking at it) bolted to the fender well. so if the relay and fuse is good, you cannot go any further without a scan tool . hope this helps and clears it up. sorry for the delay. i wish the horn system was easier. i hop you dont rate me negative because of the circumstance. let me know if you need any more info. Lou. Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! 😉
Expert:  Lou P. master tech replied 1 year ago.
I have taken my time to answer your question the best i could and i will continue to help if you need follow up information , all i ask is that you PLEASE take a second to rate my service so i may recieve my credit for assisting you. Thank you.