w204 electric seats / fuse board mystery

[Pillabenz]

Good morning. I have recently acquired a 2008 c220cdi sport with electric front seats, neither of them work and i can only find 2 fuse boxes on the vehicle, the relevant fuses seem to be in order at these fuse boxes, (but not 100% certain as info online is misleading) there is no fuseboxes behind the kickplates or sides of dash, just boot compartment and under the bonnet. I am really struggling as the seat position is affecting my breathing and making driving the vehicle very unenjoyable. Can anybody reccomend anything before i try to unbolt the seat and put a direct 12v feed to the motors to change their position, im on the larger side and having a seat set for an 8 stone woman sat completely straight is somewhat, uncomfortable. Thanks in advance. (the forward / back adjustment is on a runner so not completely the end of the world)

 

[DSM10000]

Did you know that the seats were faulty when you purchased the car?

 

[Pillabenz]

Did you know that the seats were faulty when you purchased the car?

yes i did, but as both were not working i assumed it was almost certainly a fuse but now after investigation i dont think its that simple.

 

[DSM10000]

yes i did, but as both were not working i assumed it was almost certainly a fuse but now after investigation i dont think its that simple.

Ideally you need to get a Star diagnosis to pinpoint the fault.

 

[Pillabenz]

Ideally you need to get a Star diagnosis to pinpoint the fault.

im unable to do that at present, however, i have confirmed there is power to the seat relay pins on the fuseboard in the boot relay number 6, which has blown, so i bridged the relay with some wire which got red hot and burnt out immediately, so there seems to be a large load on the electric seat relay for some reason. That is where im upto.

 

[190]

C Class W204 2008-2014 Fuse List Chart Box Location Layout Diagram – MB Medic

According to the above, there are 3 fuse boxes on a W204 and 6 fuses for the front seat adjustment 2,3,44,45,116,126

 

[Pillabenz]

C Class W204 2008-2014 Fuse List Chart Box Location Layout Diagram – MB Medic

According to the above, there are 3 fuse boxes on a W204 and 6 fuses for the front seat adjustment 2,3,44,45,116,126

yes, i seen that site, however i do not have a fusebox in my cabin at all, certainly not on either side of the dashboard or in the footwells, i have had all the panels off so some models may differ i think, depending on the spec. I have managed to trace the fault, it is specifically with the drivers seat as i have the passenger seat working with the relay bridged and the fuse for drivers seat removed, if i add the drivers seat fuse back in the mix, the bridging wire wants to turn into molten metal, i am about to remove the seat and investigate which motor is causing it, i am just waiting an hour for the airbags to settle after disconnecting battery.

 

[DSM10000]

im unable to do that at present, however, i have confirmed there is power to the seat relay pins on the fuseboard in the boot relay number 6, which has blown, so i bridged the relay with some wire which got red hot and burnt out immediately, so there seems to be a large load on the electric seat relay for some reason. That is where im upto.

You may have a damaged SAM and could have caused further damage by trying to jump terminals.

Do you have access to any diagnostics systems?

 

[190]

yes, i seen that site, however i do not have a fusebox in my cabin at all, certainly not on either side of the dashboard or in the footwells, i have had all the panels off so some models may differ i think, depending on the spec. I have managed to trace the fault, it is specifically with the drivers seat as i have the passenger seat working with the relay bridged and the fuse for drivers seat removed, if i add the drivers seat fuse back in the mix, the bridging wire wants to turn into molten metal, i am about to remove the seat and investigate which motor is causing it, i am just waiting an hour for the airbags to settle after disconnecting battery.

I know that's a US based web site but my UK drivers handbook that came with the car shows a fuse box in the same place on the drivers side. Instructions to access that triangular panel are:

open the drivers door

pull out the cover slightly at the bottom

pull cover outwards and remove it.

Possibly it's easier said than done and confusingly the photo in the handbook shows a left hand drive car but I suspect if there is a fuse box it will always be on the drivers side because there is an air bag in that cavity on the the passenger side.

 

[Pillabenz]

I know that's a US based web site but my UK drivers handbook that came with the car shows a fuse box in the same place on the drivers side. Instructions to access that triangular panel are:

open the drivers door

pull out the cover slightly at the bottom

pull cover outwards and remove it.

Possibly it's easier said than done and confusingly the photo in the handbook shows a left hand drive car but I suspect if there is a fuse box it will always be on the drivers side because there is an air bag in that cavity on the the passenger side.

Honestly, i had it open twice, there is a square void where a fusebox would be, definitely nothing there.

 

[Pillabenz]

You may have a damaged SAM and could have caused further damage by trying to jump terminals.

Do you have access to any diagnostics systems?

Nothing that sophisticated for this vehicle unfortunately. There is 3 plugs into the seat adjustment switches on side bolster, a black, a blue and a white, the black and blue i ran straight from a seperate 12v source at the plugs, this allowed me to set the seat height and recline angle, the white one was dead, so whatever the white one was is the issue i think. My seat is set and the passenger seat is working now so all is fine. Didnt realise the seats were so complicated until i removed it. Cant imagine what it would of cost at a Mercedes dealer to repair all that. !!
Thanks all.

 

[DSM10000]

Nothing that sophisticated for this vehicle unfortunately. There is 3 plugs into the seat adjustment switches on side bolster, a black, a blue and a white, the black and blue i ran straight from a seperate 12v source at the plugs, this allowed me to set the seat height and recline angle, the white one was dead, so whatever the white one was is the issue i think. My seat is set and the passenger seat is working now so all is fine. Didnt realise the seats were so complicated until i removed it. Cant imagine what it would of cost at a Mercedes dealer to repair all that. !!
Thanks all.

A good days work.

I hope you have rewarded yourself with a suitable libation!

 

[Merc59]

yes, i seen that site, however i do not have a fusebox in my cabin at all, certainly not on either side of the dashboard or in the footwells, i have had all the panels off so some models may differ i think, depending on the spec. I have managed to trace the fault, it is specifically with the drivers seat as i have the passenger seat working with the relay bridged and the fuse for drivers seat removed, if i add the drivers seat fuse back in the mix, the bridging wire wants to turn into molten metal, i am about to remove the seat and investigate which motor is causing it, i am just waiting an hour for the airbags to settle after disconnecting battery.

My 2008 C320 also doesn't have a fuse panel on the dash side as I went looking for it to find a supply for my dash cam. It may be UK models don't have them?