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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #1
I drove my car yesterday and noticed the SRS light was on. Also my aftermarket radio would not work, although there was power to it because the CD eject button would light when pressed....just no FM radio.
I read all the posts on the SRS seat sensor replacement. Looked in the fuse box and the 10amp fuse that controls the radio/side air bags{slot12 or 13?} was blown so I replaced it and started the car.....still has SRS light and radio doesn't work. Rechecked the fuse and it is blown again.
I figure the radio wiring cant be bad because there is power to it so must be the side air bags??
Maybe the radio is bad and it is just a coincidence that it stopped working at the same time?
I used an Acton code checker and no codes show up. I know this unit wont read all MB codes.
Any ideas?
Thanks
John
 

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E420 1997
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757 Posts
Since it's an easy step and it has been replaced the first thing I'd do is disconnect the radio and retry. Maybe a wire got nicked on something during the install, so inspect the wiring after you unplug it from radio and check closely.
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #3
Since it's an easy step and it has been replaced the first thing I'd do is disconnect the radio and retry. Maybe a wire got nicked on something during the install, so inspect the wiring after you unplug it from radio and check closely.
ddaddy,

Bingo!
Disconnected the wire harness from the back of the JVC radio. Replaced the 10 amp fuse in slot#13, started the car and the SRS light went out; fuse did not blow again. I'm thinking that there is an internal fault in the radio because there was power to the radio; it just wouldn't play. If it had been a shorted wire somewhere, then there shouldn't have been any power to the radio.

Thanks
John
 

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E420 1997
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Glad to hear John. BTW, the radio has more than 1 power lead going to it and on different fuses. Maybe your radio is under warrenty?

Cheers,
Ken
 

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2013 E350 Bluetec; 1985 300TD
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185 Posts
Discussion Starter #5
Well, I spoke too soon. :(
After disconnecting the radio and seeing that the{side air bag#13} SRS/Radio fuse no longer would blow, I figured I had an internal short in the radio so I bought a new JVC and had it installed. It worked fine last night and this morning. Got in the car after work, started it and the radio wouldn't work! SRS light was back on also. I disconnected the radio and replaced the fuse figuring that would fix it again. No such luck. Even with the radio disconnected, the fuse blows immediately. It will blow just by turning the ignition to the on position without even starting the car. I'm stumped. It is an intermittent fault so I'm thinking a shorted wire someplace?
Also, the #13 fuse is labeled Side Air Bags/Radio.....would this circuit be the one that is linked to the passenger seat sensor? Could this be a seat sensor issue all along? Any other ideas?
Thanks
John
 

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E420 1997
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Could be but I'd be looking for a wire in the radio compartment that got insulation stripped and is shorting on the chassis. I'll have a look at the schematic and post for you.

Look here

Pull your dome light and try again. It's not the dome light (very unlikely) but this will give you an amp or 2 more availability on the 10 amp fuse. Just trying to get down to which system. Still most likely radio IMO since that is what was changed and you got mixed results removing it (check wiring and connector very good especially where wire go into the plug that plugs into the radio.

And does someone know where the airbag sensor is? All I know is they are supposed to be on bumper with gold contacts but a good thing to check and use a process of elimination by disconnecting circuits.
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #7
Thanks Ken,
I checked for shorted wires and found nothing. Also doesn't make sense since I pull into a parking spot with the radio playing....shut off the car and then when I get back in and turn the key, the fuse blows. No movement of the car so no way for a shorted wire to shift and make contact that I can see. Its weird....could a battery that's due for replacement cause it? Maybe a voltage drain when the key is turned on from a less than adequate battery? Could voltage variation cause the fuse to blow?
I was briefly tempted to try a 15 amp fuse in that slot out of frustration but my better judgement told me not to. :eek:
 

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E420 1997
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Don't do the 15 amp fuse, let's begin by disconnecting stuff. Check the below red circled in red for frayed/bad wires, then we'll disconnect them to see if that solves it. About the only ting we won't be able to disconnect easily will be the srs module. Make sense?


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So to recap. disconnect things 1 at a time to see if fuse quits blowing.
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #9
Will do tomorrow afternoon and post what I find.....I ran out of 10 amp fuses
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #10
I disconnected all the plugs{3} under the passenger seat and it still blows the fuse. Two of the plugs were probably for the electric motor but I would guess the other was for the air bag sensor?

The airbag module looks like its behind the ashtray and has probably 30 wires coming out of it. I dont see any plug in connectors but I havent removed it yet from the console.
I may have to bite the bullet and go to the stealer :mad: for the codes to be read.
It puzzles me that I had this fixed by unplugging the radio, changing the fuse and it worked fine. Installed new radio.....worked fine.....start car a day later and fuse blows....now I cant get it to work at all :banghead:

Best car I've ever owned but a pain to trace electrical problems
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #11
A few questions for the forum:
From reading the stickies:
When the passenger seat sensor goes bad, you get the SRS light on the dash. New seat sensor and problem fixed.... BUT, when this happens and the sensor is bad....does it also blow #13 fuse?
#13 blows and is labeled side air bags/radio. Its not the radio because it worked for a short period of time after replacing the fuse.
The only SRS control module I have found is behind the ashtray. Does this module control ALL the airbags including door side bags or are there other modules somewhere that I can check.
Thanks
John
 

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Here's all the schematics.

Fuse 13 feeds front dome light, instrument cluster, radio and airbag sensors according to power distribution.

The SRS schematic shows it also goes to the srs module if it's a late production model and the seat sensor if you have the automatic child recognition feature.

Your simply going to have to disconnect these systems 1 at a time until you find the culprit. With them disconnected it will not blow a fuse unless a wire is shorting to chassis somewhere.

GL and keep us posted.
 

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2013 E350 Bluetec; 1985 300TD
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Discussion Starter #13
Fuse 13 doesn't seem to feed the dome light because the dome light is on even with the fuse blown/removed; unless I am missing something. Instrument cluster also lights up and works so I have to believe that 13 controls just radio and SRS as labeled on fuse box.
I will keep at it until I cant trace the wiring any further; then I guess I will have to pay the piper and get it scanned.

Thanks
John
 

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Discussion Starter #14
This is the most frustrating problem I have encountered with this car. Took the car to the Indie and he read the codes. The only codes were 032 & 033 which he explained were "communication interference" issues. So, he unplugs the JVC connector from the MB radio wiring connector, puts in a new fuse and the SRS light goes out and #13 fuse doesn't blow. He goes all the way down to a 4 amp fuse in #13 and it still doesn't blow!
I head over to the radio shop and we hook up the JVC back into the MB harness and the radio works fine. I drive the car for several days with no problem. Park the car this morning....turn off the radio and the car. Come out this afternoon, start the car and the fuse blows :banghead:
Go home, disconnect the radio, replace the fuse and it still blows with ignition turned to on position. I cant figure this out no matter what....it doesn't make sense. If it was an intermittent short....why would it decide to short out with the car stationary in a parking lot?
Like I said...this is one of the nicest riding cars I have ever owned but this is borderline ridiculous and nobody can figure it out. I'm not going to the dealer because I am sure it will cost more than the car is worth.
Anyone have any ideas at all? Nobody has been able to find a short in the wiring.
:surrender:
 

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I drove my car yesterday and noticed the SRS light was on. Also my aftermarket radio would not work, although there was power to it because the CD eject button would light when pressed....just no FM radio.
I read all the posts on the SRS seat sensor replacement. Looked in the fuse box and the 10amp fuse that controls the radio/side air bags{slot12 or 13?} was blown so I replaced it and started the car.....still has SRS light and radio doesn't work. Rechecked the fuse and it is blown again.
I figure the radio wiring cant be bad because there is power to it so must be the side air bags??
Maybe the radio is bad and it is just a coincidence that it stopped working at the same time?
I used an Acton code checker and no codes show up. I know this unit wont read all MB codes.
Any ideas?
Thanks
John
 

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1998 E320 base sedan @ 160kmiles
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7,215 Posts
All.

It removes the power from the module for the airbags, restraints (safety belt squibs) and sensors.

If the module is not powered, it will not control the SRS bulb.

Please include the model and model year of your car in your profile.
 

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Ok thank you. This is a 2000 E430 and the SRS light is on. When I pull the #13 fuse the light satays on...when I pull the #10 it goes out. I was wondering (hoping actually) if the front airbags were on one circuit and the side airbags on another...ie. the #10, so I could just disable the side bags...
P.
 

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1998 E320 base sedan @ 160kmiles
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7,215 Posts
All airbags and the seatbelt tensioner squibs are activated by the same module (N2/7). There are no separate modules or circuits with different fuses.

Both fuse 13 and 10 power the control module. Fuse 13 powers the module when the ignition key is in position 1 (accessories) and 2 (run), and fuse 10 powers the module in position 2 (run). So when you remove fuse 10 you are affecting the whole system. Note that these fuse designations are for 2000 year and beyond. Before that, they are reversed in functions.

I would just get the codes scanned, and find out exactly what the problem is. It could be the passenger child seat sensor issue, or it could be something more serious. If it is a passenger seat issue, you could buy an emulator for $40 or less to get rid of the SRS light. But get the airbag codes scanned first.
 
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