2003 W163 Electrical niggle

[Mike47]

Hi all,

I have a 2003 ML350 (petrol) and have a very annoying problem with the cars electrics.


The problem is intermittent and is as follows.


Sometimes the heated seat buttons light up (one light only) both seat switches are doing this. The heated don't work during this time and the switch is not responding when I try to turn it off. At the same time I have noticed that the Cruise control no longer works. Sometimes if I turn the engine off and restart the problem goes away and the seats and cruise control operate as they should.


I have a diagnostic computer check done by a mobile company called "Scantec" and no issues where found.


I might add that I've only had the car for six weeks and on the first day I got it I did smell an electrical burning. Not sure where it was coming from. I haven't smelt anything since. The car had been standing for a good few months before I purchased it.


My thoughts where it could be a problem with the electrics behind the steering wheel. Where the cruise control stalk is. The burning could have come from there. Also just noticed another issue. even when the key is not in the ignition and I turn the light switch stalk on the dashboard lights come on just like if the key had been put in and turned to position two.
When I do put the key in and turn it the problem goes away.

Any help, advice or ideas as to what my problem might be would be much appreciated.


Thanks

Mike

 

[Merc Owner 2B]

Hi there.

Sounds like a SAM unit but you need someone a bit more knowledgable to confirm and advise best course of action.

Paul

 

[Mike47]

Hi Paul,

Thanks for that.

Just had to look up what a "sam" unit is but sounds like a good place to start.

There are two fuse boxes one in the engine bay and in the Drivers footwell. i will have a look and see if the electrics that are giving me this issue are contected to the same box.

 

[Merc Owner 2B]

Has the car been through deep water recently? You may not know if you haven't had it long

 

[Mike47]

There are no signs of that. The interior is dry and smells dry. So I doubt it.

 

[Jane270ML]

Check/replace the large square fuse attached to the +positive post on the battery.

Item No 22 on here... Êàòàëîã MERCEDES

Only from MB

 

[Mike47]

Thanks for that "Jane270ML"

Will check that out.

 

[Mike47]

I've just checked and I don't have a fuse there. Could this be the problem?

Do you know what this fuse is for please?

 

[Merc Owner 2B]

I don't know if this will help.......


Both Heated Seats not working ?? - Page 2 - Mercedes-Benz Forum

Particularly this bit as it's already been mentioned by Jane270ml


"Had similar problem. Switch for heated seats would illuminate then flash but seats not working. Found the fuse on the battery pillar to be failed. Replaced and all worked. The fuse is square between two cables on positive term of battery, doesn't look like a fuse at 1st glance. Worth checking. "

 

[Merc Owner 2B]

Just going back to basics.......... are you sure the battery is OK? I never fail to be surprised at the so called "faults" a poor battery can throw up.

 

[Mike47]

Thanks I will phone Mercedes and order a fuse.

I've just had a new battery fitted by the rAc, so rules that one out.

 

[Mike47]

update :

I just phoned Mercedes main dealer and gave Chassis number and my car doesn't have or need a fuse on the battery terminal, so that rules that out.

The guy I spoke to had never heard of any of the problems I mentioned. He could only suggest booking it in for a look but at thier prices I will give that a miss.

He did say (might be of interest to anyone who has a W163) that the Cruise control does have an ongoing fault that is still coved by the Mercedes warranty. Even though my car is 10 years old and has 121k miles on the clock. I will phone tomorrow and speak to the warranty man. (He only works part time)

So looks like I'm going to have to live with my issues. I can still get from A to B in it. So not the end of the world.

 

[frog1520]

Thanks I will phone Mercedes and order a fuse.

I've just had a new battery fitted by the rAc, so rules that one out.

Did the RAC fit the right battery?

Did you have the problem with the old battery as well, or just since the new one was fitted?