SL/R230: Battery discharge via horn sensor
07-27-2015, 08:50 AM
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clk 320, SL500
Battery discharge via horn sensor
Howdy to All, I have a 2005 SL500 which I keep a battery tender on the convenience battery when not in use which never shows fully charged. I brought it in to dealer for the A service asked them about my charging concern. After they checked, I was told that the horn sensor was bad and needed to be replace even though the horn works. That the cars' system keeps consistently checking with no response from horn sensor. that although its a very low voltage use that it does discharge the battery with time. ~ 500+ to replace. I've checked the forum and although a lot has been said on the topic of battery discharged, I can't find any thing with horn sensor issue? Any Input would be appreciated. Thank You
07-27-2015, 08:03 PM
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I have said this a few times to others as this happened to me. I found that the starter battery was going bad and the "convenience" battery was trying to top it up via a DC/DC converter and running the convenience battery down and would go into the limited use mode.
Worth disconnecting the starter battery and testing it.
Worth disconnecting the starter battery and testing it.
07-27-2015, 09:01 PM
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clk 320, SL500
Well that may be part of my problem! I had brought the car to the dealer 3 months age when I got the car from a good friend to have it checked out. At the time I was told that it needed a starter battery (which my friend agrees with), motor mounts and a left strut torque as well as front disk break /pads which I held off. So to my surprise when they did the A service and checked the car all was good. It got a clean bill of health! The only thing was the horn sensor was bad. So here I am trying to make sense of it all. I will have the starter battery check to confirm condition as you say. Is there such a thing as a horn sensor and draining the battery when car isn't driven regularly?
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08-01-2015, 01:37 PM
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clk 320, SL500
Well today I went to an Indy to get a systems diagnostic check. He did confirm that BE67 Alarm Horn, Anti Thief needed to be replaced(an easy way to test this, when you turn the car off and you don't hear the beep its bad). I was told that its a common issue. The system is not allowed to sleep and drains the battery I had him replace it for $335 including tax. A load battery test showed both battery's to be good. I will let you know if the battery tender give me the green light when battery is charged. As for the other issues that I had, he did confirm Motor mount was starting to weep. That there was no hurry at this time to replace. Front disc brake/pad still had some life but should be replaced but no hurry. As for the strut torque, the bushing was worn and should be replaced but no hurry.
