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2005 s500 4Matic
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Discussion Starter #1
Hi guys

just today i decided to replace the important relays on my 2005 s500 4matic
I had issues with fuse for my heater blower recently and I decided to be proactive and change out important relays before they left me stuck somewhere
I changed the starter relay L and chasis relay L under the hood passenger side fuse box and the fuel pump relay under the rear seat fuse box.
Now I have no crank at all and the power windows do not work nor does the above head fan and I cant shift out of park either. I think this is a electrical related sinbce the car was perfect up to today

PLEASE help with any suggestions,
 

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2003 S500
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Reverse what you did, double- and triple-checking to be certain that you installed the correct type of non-Chinese relays in the correct sockets.

If that doesn't help, check the battery and its connections. If no help there, check the main pre-fuses under the aluminum cover under the passenger's toe-board carpet. If no help there, check the main fuses under the trunk lining just forward of the battery.
 

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2005 s500 4Matic
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Discussion Starter #3
Hi Wally

I replaced 3 or 4 relays with HELLA brand and tried back tracking..disconnecting battery but same thing. I get no power it seems even with the key turned to run position the dash goes black
It seems to be somethings that controls electrical to dash and seats
 

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2005 s500 4Matic
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Discussion Starter #4
I have checked fuses for the ecm 78 and control unit 83...on the passenger side dash and they both worked. Neither power seat works....the dash lights up when i open the door but goes dark after a while. The heat/ac control unit does not light up when I turn the key so I dont think this is related to the gear shift lever or the key. I tried my spare key but it doesnt work either, The dash doesnt seem to respond when I turn the key to the on or run position and I cant shift out of park so I guess the shift interlock is not impacting by this too. I simply removed a few relays and replaced them with new ones. The starter relay, fuel pump relay, chassis relay, suspension pump relay were replaced today. Not sure what else to look for. I did leave the battery connected while I was replacing the relays buy the replacement was simple with no sparks. Im not sure if removing some of the relays could have created an issue with some module. Should I leave the battery disconnected overnight?
 

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You probably blew the Main prefuses under passenger floor. Disconnect battery, put In all the old relays back where they were and check prefuses
 

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Discussion Starter #6
Hi Tusabes
Thanks so much for the reply

I have not checked the prefuses yet...I thought that since the important fuses..ecm , chassis were getting 12 volts the main fuses were ok..but I guess its possible they were damaged. Oddly when i was replacing the relays....nothing shorted or so i think. But since the key does turn when inserted...the EIS must be fine since it recognizes my keys and allows them to turn. The dash light do come on when I open the door so I think that means the SAM is ok as well. There was no water intrusion here...just me replacing relays while the battery was connected.
I will have to check the prefuses on the pass footwell
 

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W220 Moderator
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It is likely that disconnecting the battery has caused something else to fail, disconnecting it serves no useful purpose and causes tons of grief.

As above check the prefuses with a proper load, (not multimeter) use a bulb !!
 

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2010 S500
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It is likely that disconnecting the battery has caused something else to fail, discnnecting it serves no useful purpose and causes tons of grief.

You suggestion worries me. According to "the book" most of the repairs start with "disconnect the battery".
 

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Errrrm what "Book" exactly ?

There are no decent Workshop manuals for these cars unless you buy MB WIS, and that will not tell you to keep disconnecting the Battery every time you open the Bonnet etc like the old fashioned "Haynes" type Manuals do lol

I've done this to death before, hell like many specialists with MB's (and newer cars that do have lots of Electronics) I don't even power the Cars down if I need to change a Battery, I keep it alive with a Slave Battery ;)

There are specific procedures to Power Down a lot of Vehicles since about year 2000, (earlier on most MB's), and you don't just keep disconnecting the battery willy nilly ;)

Would you pull the wall plug out of your Windows 10 Computer whilst it is powered up ?

If you want to work on a specific system the answer is to just pull a relevant fuse to power it down, and also to be very careful.

If the person doing these procedures doesn't know this and is not familiar with these vehicles, then I too would be worried ;)

.
 

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W123 1985 T-model M110
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Hi guys

just today i decided to replace the important relays on my 2005 s500 4matic
I had issues with fuse for my heater blower recently and I decided to be proactive and change out important relays before they left me stuck somewhere
I changed the starter relay L and chasis relay L under the hood passenger side fuse box and the fuel pump relay under the rear seat fuse box.
Now I have no crank at all and the power windows do not work nor does the above head fan and I cant shift out of park either. I think this is a electrical related sinbce the car was perfect up to today

PLEASE help with any suggestions,
Green relay for starter is special with diod. If you replace it with another 5-leg relay, you will burn the wiring and SAM.
If need green relay need replace, just with 4 legs relay.
And one more relay have two places for mounting(for two types of control units)
Passenger side.

Отправлено с моего GM 5 Plus через Tapatalk
 

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2005 s500 4Matic
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Discussion Starter #11 (Edited by Moderator)
Hi guys

So today I found the 60 amp prefuse by the passenger side foot well blown.....I replaced it with another 60 amp fuse and when I turned the key to on...the lights worked normally and the overhead fan syarted working again but within a few seconds....the 60 amp prefuse blew again. I dont know if the issue are the relays I replaced but I dont see how. They are new HELLA brand and 3 are the 4 prong and 1 is the 5 prong for the starter relay. @Kolleso ...my old starter relay was a GREEN relay with 5 prongs and it with a black HELLA brand 5 prong I got from FCP euro. Not sure if the starter relay would cause an issue with just having the ignition in run position.
If anyone can suggest what could be causing the 60 amp fuse to blow....PLEASE suggest where I can look. I checked for pinched wires in the passenger side fuse where the relays I rep[laced and even under the seat where I replaced the fuel pump relay....all wires appear fine. I am desperate and suggest any ideas..Thanks
 

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W220 Moderator
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Hi,

@2005s5004matic

Why don't you try just putting back your original Relays, that is of course assuming you haven't already fried Module(s) and it is FUBAR Modules causing the pre Fuse to blow ??????????? ..........

Which is why I edited your above post to call @Kolleso as he knows much much more about this in his sleep on a bad day than I do ;) Believe me when I say he knows MB Electronics better than Mercedes themselves ;)

@Deplore may also be able to offer some help

HTH,
 

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I told you to put the old relays back then change the prefuse. Why do you keep insisting to use the new relay?
 

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Discussion Starter #15
Hi guys...first off thanks so much for the great information. I finally did get the car to work. After replacing the blown 60 amp prefuse...and having that one blow as well (with the new relays installed), and reading Kolleso's suggestion that the starter relay needs to be the GREEN one...I decided to replace the blown 60 amp prefuse and replaced the relays with the old ones...everything worked.
So I believe the issue was with the starter relay I was sent by FCP Euro...even though it was a 5 blade relay that was sold as a Mercedes starter relay...it could have fried my computers and I consider myself extremely lucky. As Kolleso said...the GREEN relay has a needed diode that the other versions may not.
I can't thank you ALL enough for the suggestions....disaster averted.
I love this site..
 

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FYI never proactively replace electrical parts that are working . Replacing working electrical parts is not part of “maintenance “ in these cars.

change fluids , brittle rubber hoses etc. leave the electronics alone if they work
 
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