Electrical sound from rear seat area

[Stevester 500E]

Has anyone ever had the follow or similar symptoms?
When I open the car, I hear a noise like something is on.
Seems the sound is somewhere in the rear seat area.
I have had this a while and don't remember when it started.

A while ago the horn alarm when on with no reason, so I bypassed the immobilizer by shorting two terminals at a K38 relay behind the instrument.

Any ideas? Where do I start? Any help is greatly appreciated.

Last month I solved an issue with my W124 with the help of guys on another forum. I would have never solved it on my own. In this particular case it was a bad/oxidized connection.

It seems that Mercedes have more electrical issues than I have encountered on other makes. I think the issues go beyond the blanket stated of "ecojunk" wiring.

 

[Stevester 500E]

Can anyone recommend a good MB electrical tech in San Diego.
I might just take my car in to have the whole car gone thru, as my blinkers, right parking light, and rear tail light have issues too.

 

[Glen]

Vacuum pump? Does your central locking system work correctly?

 

[Stevester 500E]

I think so, but I will look into it a little closer.
Thanks

 

[JC220]

Can anyone recommend a good MB electrical tech in San Diego.
I might just take my car in to have the whole car gone thru, as my blinkers, right parking light, and rear tail light have issues too.

If you haven't already done so I would recommend replacing all of the fuses with new Copper / Ceramic items. And also cleaning the fuse box terminals / earthing points under the hood.

Over time the original fuses suffer from corrosion and although they may look OK they can cause all sorts of electrical issues in these cars. This is something you can do yourself in half an hour and it should be done prior to further diagnosing the issues.

The only electrical item under the rear seat is the Vacuum Pump for the central locking. That is most likely what you can hear although it should not run on if the system is operating correctly.

 

[nocfn]

While I cannot attest to the W124 specific issue, the c126 got all new ground straps inside engine bay and starter/transmission. While the same numbers, the replacements were more robust gage replacing 20+ years of grease, road grime and heat cycles. The engine strap fell apart in my hands at the PS pump attachment point. Just something to consider, strong clean ground connections at all locations.

Fuel pump relay under the seat as well.

 

[Stevester 500E]

Is there a technique and tool to clean the fuse box terminals?

If you haven't already done so I would recommend replacing all of the fuses with new Copper / Ceramic items. And also cleaning the fuse box terminals / earthing points under the hood.

 

[gerryvz]

Generally the fuse terminals (the slots that each fuse fits into, inside the fuse panel) themselves don't oxidize. A "poor man's" way to do this would be to just twist each fuse back and forth in its holder to break through any oxidation on the fuse ends themselves.

The better way is to purchase new ceramic and copper or brass fuses and replace each fuse in the fuse panel.

Cheers,
Gerry

 

[JC220]

Is there a technique and tool to clean the fuse box terminals?

I only had one or two corroded terminals on the fuse box itself (A green coating at the fuse connection) I used fine emery paper & Electrical Contact Cleaner spray to give them all a quick clean before installing the new fuses.
These are the sort of new Fuses you require-


http://www.ebay.com/itm/Mercedes-Ceramic-Fuse-Set-8-16-25-AMP-Set-New-German-Flosser-/302179430016

 

[Jlaa]

I just did this. Nearly all the original aluminum conductor fuses under the hood were slightly "sticking" onto the contacts and required rotation to break through the sticking. I got 60 ceramic / copper fuses for ten bucks -

http://www.ebay.com/itm/291978559009

 

[Ascension]

If you haven't already done so I would recommend replacing all of the fuses with new Copper / Ceramic items. And also cleaning the fuse box terminals / earthing points under the hood.

Over time the original fuses suffer from corrosion and although they may look OK they can cause all sorts of electrical issues in these cars. This is something you can do yourself in half an hour and it should be done prior to further diagnosing the issues.

The only electrical item under the rear seat is the Vacuum Pump for the central locking. That is most likely what you can hear although it should not run on if the system is operating correctly.

Yep those little buggers are a real PITA!! Can look perfectly fine but will have a hairline crack that you will never see until you pull the fuse out. Then it just falls apart and becomes apparent. One of the 1st things I had to do to my E420 was replace all those little buggers. Trust me here if they have been in there for a while REPLACE THEM ALL it will save you a LOT of grief!!