Disconnect battery?

[dgbmvb]

Hi gents, going to change my glow plug relay tonight (2009 W211 E320CDI Sport), can I do it without disconnecting the battery? If I do have to disconnect are there any particular care points I should be aware of with the vehicle electronics?
Cheers!

 

[AMGeed]

No idea about whether the battery should be disconnected for this procedure or not. But if you do disconnect the battery, remove the negative terminal first and replace last.
Also be aware you may have to reset the windows and sunroof after reconnecting

 

[whitenemesis]

And then reset the windows/sunroof

 

[dgbmvb]

Re-set windows? doesn't have a sunroof so one less thing to faff with!

 

[AMGeed]

Open each window fully on the button then close and hold for 5 seconds. That resets the window opening.

 

[whitenemesis]

From the owner's handbook

The door windows must be synchronized after
the battery has been disconnected or if the
door windows cannot be fully closed (express
operation).
Each door window must be synchronized
separately.

• Close all doors.
• Switch on the ignition.
• Pull and hold switch 1, 2, 3 or 4 until the respective door window is closed.
• The door window opens again slightly.
• Pull and hold the respective switch once more immediately until the door window is completely closed.
• Hold the respective switch for approximately 1 second.
• The door window is synchronized.

 

[Diesel Benz]

Hi gents, going to change my glow plug relay tonight (2009 W211 E320CDI Sport), can I do it without disconnecting the battery? If I do have to disconnect are there any particular care points I should be aware of with the vehicle electronics?
Cheers!

I guess you have had some glow plugs changed? Most often the relay goes when a glow plug fails. If the car had a lot of miles, it would be better to change all plugs and then the glow output stage (glow plug relay).

The relay has a huge supply cable, be very careful to avoid ground contact if removing the relay without battery disconnected. The pins at the connector are however female and it would not be difficult to change the relay without disconnecting the battery.

Some MBs have SAMs that are prone to fail when the battery is disconnected, 204 should not be as sensitive as some other models though.

The attached photo shows how the wires inside the glow plug relay fail (wires from the circuit board to the relay connector).

 

[dgbmvb]

Procedure carried out without issue, thanks for all the hints and tips

 

[dgbmvb]

still got the glow plug light on for about 30secs after engine starting, indy reckons No5 glow plug showing faulty, quoted £80 to exchange that or £205 to do all 6, providing none snap! Tempted to do just the one, I know others advocate all 6 but I've tipped too much money into this over the last couple of months!