Help - Electric Seats Problem - SL320 1994 - Electric Seats

[DMWood]

The electric seats in my SL320 seem to have lost the plot. On attempting to adjust the seats in a backward direction they move forward and will not move back again. I have disconnected the battery and reconnected and occasionally this clears the problem but only for a short while. This problem is affecting both seats.

Can anybody help.

 

[Andy]

Help - Electric Seats Problem

Hi,

I would try replacing the switch. They sometimes play up internally.  Causing the problem that they will move forwards but not back and so forth.

Good luck

Regards

Andy @ www.mercedesservicing.com

 

[DMWood]

Help - Electric Seats Problem

Andy,

Thanks for the reply.

The adjustments in all three planes seat fwd/back, base tilt and rest recline (except the head rest up/down) are affected on BOTH seats. I had been thinking that may be it was a voltage supply problem?

Switches seem to work in both directions but have the effect of movement in one direction only???

They don't seem to do a Haynes manual for the SL range!!

 

[Anonymous]

Help - Electric Seats Problem

You have a missing feed at the switch bank.  You need to check the voltage supply to the switches and then trace back to where the fault is.  The motors are reversed simply by having the switches reverse the supply.  The switches are double-pole switches - you should be able to cheack-out the supply with a voltmeter.

Eric

 

[DMWood]

Help - Electric Seats Problem

Not sure about the feed problem Eric!!

Yesterday I started the car and the seats worked for the first 5 min or so and then the fault came back.

As the car is not frequently used and sits on the drive in the weather, I was wondering if the switches were damp!

I suspect the switches send low current signals to the box of tricks under the seat where these signals are used to power relays or solid state switches which control the power to the motors!!

Still funny that it is affecting both doors in identical ways though??

 

[Matt Crooke]

Help - Electric Seats Problem

Sounds like its time for a much loved can of WD40 to come out to play. if it is damp, spray the internals of the switches, that should do the trick.

 

[eric]

Help - Electric Seats Problem

"Still funny that it is affecting both doors in identical ways though??"

That's why I suggested a problem with the feed to the switches - it must be something common to both switches (or motors). A bad switch contact would affect only one seat, not both.
BTW, I suggest using something like Electrolube switch cleaner rather than WD-40.  WD-40 is not so good on switches, it tends to 'gum up'.

Eric

 

[Andy]

Help - Electric Seats Problem

Hi,

If you check your fuses. I think the seats have seperate fuses. If this IS the case. Then in my opinion its back to the switches.

All the switches do is reverse the current. So if it will only go one way then the switch is not sending the feed down the other way when operated.

Just because its happened to both dosn't mean it can't happen. Look at it this way. The osf (drivers) is used more regulary and COULD be worn. The nsf could just be sticking through lack of use. Don't dismiss the obvious and look something technical when its not there. Try the obvious first before getting involved.

I just had a chat, there is also a sensor in the pillar behind you where the B post would normally be. This sensor, senses when the back rest is coming to the end of its travel. This could also cause the problem. Ie, goes forward but not back.

Regards

Andy @ www.mercedesservicing.com

 

[DMWood]

Help - Electric Seats Problem

Andy,

I'm with you on the B Post Sensor.

This sounds like a likley cause and would explain the symptoms!

Where exactly is the sensor and what form does it take? Is it a Reed Switch? Magnet mounted on the post or seat?

Thanks all...

 

[DMWood]

Help - Electric Seats Problem

Does any body know anything about the sensors which detect the maximum reclined position of the seats??

It would be good to know how they work and where they are?

Thanks..

Dave