Rear lights staying on

[RMVS]

Hello,

I just purchased a 2008 Merc ML 320. The battery was completely dead (purchased at auction). I recharged the battery and the car has an intermittent loss of acceleration. Not too worried about this as I believe the codes point to the EGR.

However, as the vehicle sat stationary with the engine of waiting for it's MOT today the rear lights came on and won't go off. Tailight, brake light and reverse. All rear lights just remain on. I cant find anything online as to what this can be. I checked all fuse boxes and they seem dry.

Any ideas what it could be? Thanks

 

[Larkone]

Faulty SAM?

 

[richard]

Rear SAM probably got wet (or just failed). Its in the boot on the right hand side below the fusebox.

 

[optimusprime]

Damp in sam .

 

[PaulMason]

Picking up on this query, I have a similar rear light issue on my 2008 ML 320 CDI. The lights all work, but I get a message on the dash saying left brake light and right brake lights not working. The iCarsoft code is under a Rear SAM fault and reads "component E3e4 (left stop lamp) or line to component has a short circuit to ground" (another for the right light too). I isolated the tow bar wiring as the splices looked a little iffy and a couple of wires were nicked so the wiring visible through the sheath. No change to fault . I then pulled the sockets holding the brake light bulbs and they appeared to have some tinfoil to account for broken connectors. I swapped them with the reversing lights to see if that was the issue. Fault code remained. So I am now a bit puzzled and have 2 questions:

1) Should an ML have a 2 filament stop and tail bulb (they ones in are single filament and the 4 tail lights come on and then the inner 2 get brighter when the brake is pressed (plus the 3rd high level light)? Is the socket for the stop and tail different to the other ones in the rear unit (tail only or reversing light)
2) Does anyone know the correct part number for the rear SAM - mine is A164 540 23 01. The Delphi part number is 28140774. The previous owner said it had been replaced and I am wondering whether the replacement SAM is wrong hence the fault.

As I say, the lights are all working fine and as they should. I am going to remove the units and clean all the connectors and earth as well as also get some replacement sockets as at least 2 have been "modified" with tin foil!!

Thanks as ever in advance for your wisdom and guidance

 

[Trickythemerc]

There are two types of stop and tail lamp bulbs 12v 21/5w and 12v 21/4w both have different offset on the pins that locate in the socket. You can also have single filament 21w with separate 5w tail lamp bulbs. Put your reg in autobulbs web page and it should show you which bulbs you need.

 

[OneForTheRoad]

Single filament bulbs normally fit into a single contact bulb holder , dual filament bulb holders have 2 connections inside as does the bulb on the bottom. The offset pins are there to help avoid incorrect fitting. But it's still possible.

 

[PaulMason]

Having looked, all of the holders (except indicators) appear to be the same, all have P21 bulb and are marked P199345. Unfortunately I don't think the holders or bulbs are the issue (as I say all of the lights are working, it's just a damned code being thrown and a warning on the dash)

 

[OneForTheRoad]

Having looked, all of the holders (except indicators) appear to be the same, all have P21 bulb and are marked P199345. Unfortunately I don't thing the holders or bulbs are the issue (as I say all of the lights are working, it's just a damned code being thrown and a warning on the dash)

If it's just the brake lights in question maybe consider changing the brake light switch. They're cheap enough.

 

[PaulMason]

Would that trigger a fault do you think, even though the lights are coming on?

 

[OneForTheRoad]

Would that trigger a fault do you think, even though the lights are coming on?

It's either that or change the bulbs along with new bulb holders. W211's were notorious for this issue on the rear number plate bulbs.

 

[PaulMason]

This may sound like a daft question, but which of the lights on an ML should come on for the brake light - just seen a video on youtube and it was the very top light whereas on my car the 2 lights at the bottom come on for tail lights and then the inner one on each side (under the reversing light, next to the tailgate) are the ones which brighten for the brakes?