mwolf5682

I did a search so forgive me if I missed something. Went through 400 posts on back up light and reverse light found nothing.

2009 ml 350 4 matic: Reverse light/Backup light will not turn off. Key out, car shut down, light is on. Warning on cluster says left reverse light. Tried shifting in and out of reverse many times, thinking a stuck switch. No luck.

Since light will not turn off, removed bulb and replaced to see if breaking current would help, no fix.

Any suggestions? Why only left (drivers side bulb on)? If switch faulty, can it fail on one side only?

Any suggestions would be appreciated.

Thanks

kombifan

Check for water intrusion at the rear Sam. If it feels wet let us know.

mwolf5682

Thank you Kombi, I will check, it has been raining. Its a whole new ball game with that tip. I was hoping it was something that was perhaps a bit simpler, a stuck relay or switch.

Would there be any other symptoms to expect? It did have a long start sequence yesterday with continued cranking but no start. Second attempt it fired right up as usual. Gremlins.

The rear sam is on the right side under the little rubber mat covering it up (weather protection) eh? Will start down that trail of fun this afternoon.

kombifan

Depends on how e much water got in

mwolf5682

Well, inspection completed. The covering carpet like rubber backed sheet on top of the SAM was wet on top. The back side of the sheet was dry. The SAM itself appears to be dry, have not removed it at this stage.

Looks like I will have to spend some time figuring out the SAM and water intrusion, I know that it is an issue, but thought it was corrected by 2009 model. Would hooking up a code reader that can read MB codes give me any further info?

Thanks

kombifan

Yes. A code reader will help.

But you'll have to go further and look at the sam to really rule out corrosion. Also check the front Sam for water intrusion.

Also. (Lots of also) check out the tail light seal. Remove the tail light and check if the seal is placed on the taillight or on the body. If the seal is on the tailigith you need to purchase new ones and install those too.

mwolf5682

It is interesting indeed. Read the UK MB club thread on where the leak comes from. No consensus, sounds like third brake light leak runs down tail gate into boot area, tail light seal as you mentioned, and possibly window seal in rear quarter. What a drag. Can one bag up the module some how to keep it dry? I know its got many connectors but if water intrusion is from bottom, would sealing it somehow make it more robust?

I will remove SAM and take a closer look. Since rear tail lights (whole) are connected to rear SAM it seems most likely.

The tail light seal should stay on the body when light removed? Was there a part change on the seal?

Sadly, if I replace the module, I will need to have it reprogramed? I really do not like the dependance on the dealer to wave the magic wand after parts replacement, but not sure of any work around.

Not sure why, but replacing the SAM is not that onerous, but having to visit the workshop to reprogram seems like a real insult. Just me, old man yelling at clouds.

Thank you for your attention to this matter, its much appreciated.

texterted

Don't put it in a bag, it'll make it sweat and corrode worse!

I've saved up every bag of silicon gel that I've come across. They don't go in the bin in my house, they go in the two SAM areas and in the tailgate pump cavity.

mwolf5682

Thanks for the silica tip. I do not have any of those bags, but may have to go to the shoe store and pick some out of the Nike boxes. Its a long trip from China by sea.

I talked to a local shop about reprograming if I replaced module, and the mechanic said he does not reprogram rather buys used ones and that they are close enough to work without reprogram. Does this make sense?

I thought maybe the key remote system etc. was involved, but that may not be correct. I would love to go the used route if I can avoid reprogramming. Otherwise the lifetime warranted part from FCP seems like the way to go.

texterted

I only thought it needed programming to suit particular options. For instance to enable trailer functions after adding the necessary relay.

mwolf5682

Not sure, all the new ones say they need to be programmed. I like your desiccant idea, more and more. Talking with a shop tech, he said part of the problem is condensation , which makes sense in a warm garage in our Minnesota climate. Condensation is an unlimited supply of moisture.

Maj. Dundee

Yes, I agree.

mwolf5682

Well, I have removed the rear SAM, things are actually pretty tidy back there. There was moisture but no rust, will replace light seals just for caution.

Opened up SAM and sure enough there was corrosion on one of the connector sockets also on a multi prong chip. Not bad, a little baking soda, alcohol and fine brushing removed all visible corrosion. The whole board did not look bad at all, and the corroded pins in the socket are probably due to water that ran down the wires and into the connector and up on to the prongs by capillary action.

With great anticipation, cleaned, and reinstalled. Reverse light is still on, and the rear hatch does not operate now. I suspect that the board has been damaged due to shorting out by corrosion? Not sure the status on the rear hatch, but inspected the motor under the spare tire, it was pristine living in its foam lined housing. Hoping that a new SAM will remedy the faults. I ordered a new one, and will report back on its installation.

At question is does it need to be programmed. My model does not use all of the sockets on the current SAM so there must be additional inputs etc. not utilized in our model. Here is hoping it is a simple swap and play.

Maj. Dundee

If it's a virgin SAM, yes it must be programmed.

If it's a used one with the same part #, it will start the veh. and will only need programming if it does not have the same options.

mwolf5682

Report from the driveway. New MB rear SAM arrived from FCP today. Lifetime guarantee and they claim they will replace when it fails, so this may be the best solution to fighting any slow creep corrosion etc. Did get some new tailight seals nice and squishy and foamy.

Disconnected battery, plugged in new SAM. Held my breath. Tail gate closes. Door switch, driver door switch and key fob all work. Left rear backup light no longer is on. Third brake light error on dash along with rear back up light error is gone. Car starts, drives.

This was a brand new MB part. I am hoping no programming will be needed. Will keep you posted.

God I love the feeling when its something you can diagnose and correct by yourself. Lets hope this holds.

Thanks for everyones input. Much appreciated and very enlightening. Hope this helps someone else coming down the trail.

kombifan

Glad it worked out!

texterted

That's a result then!

Maj. Dundee

Get new tail lamp seals or else this will happen again.

mwolf5682

New tail light seals are on the work bench. Funny, die cut foam with adhesive on one side, what happened to molded rubber? I assume the adhesive is applied to the sheet metal and not the plastic. Gasket is stuck to the body?

Its interesting, the concept that this will happen again. It's most likely guaranteed it will happen again. But hopefully not for another 10 yrs. It is interesting how engineering weaknesses are not corrected by replacing parts unless new parts have been revised properly. Restoring it to its showroom condition will guarantee it will happen again.

Thanks guys.

Maj. Dundee

Yes the gasket should be applied to the body opening.

What I meant by it will happen again, was the leaks will occur again if the seals were not replaced.

mwolf5682

I hear you about the seals. What I meant was the car left the showroom with new seals and they eventually failed. So even with everything back in tip top shape, there will be failure in the future. Every ten years is something I can live with.

How would I improve the design? Maybe hang the SAM vertically like the fuse box so water or condensation drips down and cannot collect in the plug/sockets or board.

The back fender well is clean, little to no corrosion, so the water accumulation must be very little. The tricky part is it likes to travel on the wires which is right into the pugs and then the board.

kombifan

The seals came from the factory attached to the light housing.

The proper way to do it is to attach it to the body.

The leak will not happen again.

mwolf5682

Thanks Kombi, gonna stick them on this week.

How is your ML55? I sort of like our old w163 better than the w164. Seems like its more robust and less frills, but time will tell. The size is just a bit more compact and efficient I think. Here in Minnesota both are great in the winter, but the w163 just seems like it was born for the snowy North.

kombifan

Eh.

We also have a 10 gl. Which is the same platform as the as w164;

Everytime we drive that car it is smooth and comfortable. It drives like a car. Really nice especially with the v8.

When driving the ml55, it's definitely another beast. It drives like a truck, it's a rougher ride and it's loud.

Love it.

We drive up north often and have winter tires on the gl, definitely the gl is more at home in the snow than the w163. But that may be a perspective thing.