Location of relays
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Joined: May 2020
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08 Mercury Milan
Location of relays
I'm working on yet another friends Mercedes... a 97 Mercedes S320 (W140 Class). The problem on this gem is that the horns do not work. I've removed the horns from the vehicle and hot wired them both to see if they work... and they do. My next step is to test light circuits at both horns to check the grounds and the hot feeds. My thoughts are that I won't get any feed but my grounds will be fine which will lead me to the horn relay.(I already checked the fuse in the fuse box and it is well). Assuming I can figure out where the relays are located and a diagram of what each relay controls, I'll be golden. The question of the day is, who is going to be that one outstanding person to help me out?
I've read elsewhere on the Internet that the relay box is located UNDERNEATH the fuse box on this particular car. If so, how would one access the relays with all the wiring of the fuses above the relays in the way?
Any help with diagrams, physical locations, troubleshooting tips, etc to help my buddy fix his horns will be greatly appreciated. One of the reasons I took the horns out in the first place was that I had the lower dust shield off for some underbody maintenance anyhow so it was easy enough to remove the horns with the tires off, PLUS, MANY sites suggested that 75% of the time, the horns were bad and needed replacing... so I said what the heck, their bad anyhow. So now I'm at a point where I have a bad relay, bad horn switch or some bad wiring somewhere... we'll see.
Thanks everyone.
I've read elsewhere on the Internet that the relay box is located UNDERNEATH the fuse box on this particular car. If so, how would one access the relays with all the wiring of the fuses above the relays in the way?
Any help with diagrams, physical locations, troubleshooting tips, etc to help my buddy fix his horns will be greatly appreciated. One of the reasons I took the horns out in the first place was that I had the lower dust shield off for some underbody maintenance anyhow so it was easy enough to remove the horns with the tires off, PLUS, MANY sites suggested that 75% of the time, the horns were bad and needed replacing... so I said what the heck, their bad anyhow. So now I'm at a point where I have a bad relay, bad horn switch or some bad wiring somewhere... we'll see.
Thanks everyone.
Thread Starter
Newbie
Joined: May 2020
Posts: 14
Likes: 0
08 Mercury Milan
Yep you are trapped by the FUYAA. Change everything you can change regardless if it corrects the problem or not. First of all get your friend to subscribe to MB WIS all the wiring diagrams for your VIN are included. Plus your info about the horns does not hold up. Most of the issues with the older horns are corroded connections and faulty grounds. Then the relays which may or not be there depending on the VIN's wiring diagram. Continue on, have fun!!
... In regards to my buddies horns it looks like someone had replaced them in the past... both of them are the same frequency. Once I bolted and wired them both back up, I jumpered the relay and they both worked, confirming that at least the power and wiring to the horns is in good shape. I disassembled the crap under the steering wheel and discovered that all the insulation that is supposed to be fastened tightly to "whatever", has actually managed to wrap itself around the actual steering column. In all likelyhood, the last yahoo under the dash failed to realize his haphazard efforts would likely cause damage such as wire tugs and pulls. My thoughts at this time are that I'll find at least the horn wire disconnected from the main harness and I'll need to initiate a repair to get 'em working again.Thanks for the suggestion on the subscription to MB WIS. It'll be $120 for the year, but I'll try it for a couple months to make sure I like it first. Outwardly, it looks really good.
Thread Starter
Newbie
Joined: May 2020
Posts: 14
Likes: 0
08 Mercury Milan
Yep you are trapped by the FUYAA. Change everything you can change regardless if it corrects the problem or not. First of all get your friend to subscribe to MB WIS all the wiring diagrams for your VIN are included. Plus your info about the horns does not hold up. Most of the issues with the older horns are corroded connections and faulty grounds. Then the relays which may or not be there depending on the VIN's wiring diagram. Continue on, have fun!!
Thanks.
