W164 trailer lights not working?

[Hussnainh8]

Hello guys

I have issue on my ml320 2008. Tried a trailer light board (no lights), tried my old trailer which has standard bulbs (no lights) and then I tried my new trailer which has dynamic led lights (from eBay, getting power to indicators so sweeping indicators but they are always on and I can't stop them without disconnecting the 7 pin plug. No tail lights or brake lights working on trailer just the sweeping indicators constantly on and can't turn off without disconnecting plug. I am imaging its a issue with my SAM but want to know definitely before wasting money. I am also wondering if there is a alternative solution such as to buy a bypass box of eBay and rewire the trailer socket to my tail light? Would that work without upsetting the electrics in the car?

Thanks.

 

[Hussnainh8]

Can see little water on rear sam, fuel gauge also not accurate and error codes showing for rear sam short circuit/open circuit etc.. could it be the rear sam that's partially faulty?

 

[Hussnainh8]

IMG_20221121_144018.jpg

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[JHS]

Can see little water on rear sam, fuel gauge also not accurate and error codes showing for rear sam short circuit/open circuit etc.. could it be the rear sam that's partially faulty?

With a list of error codes, there is a good chance that it is faulty, otherwise you would not have error codes!

 

[AndrewOl]

The W164 is known for water ingress in this area damaging the Sam. You may be lucky and be able to save it. If you get it out dry it off and look for any verdigris, clean it off and give it a go. The water usually comes in around the tail lights when the gasket gets old and leaks.

 

[Hussnainh8]

Gave it a go and attempted cleaning the sam. Tbh it wasn't too much ingressed but alcohol and electric cleaner cleaned it right off .. saying that it hasn't done anything to fix the fuel gauge codes and neither are my trailer lights working still (still only getting the indicators sweeping) so I do not think the Sam is the problem here.

 

[Deesidecars7]

having had an ML320, i had the same problems and they just got worse until i changed the rear sam unit, got a merc indy to do it, also got rear light seals renewed,

 

[JHS]

Mercedes SAM – Signal Acquisition Module Explained – MB Medic

www.mercedesmedic.com

Your symptoms are here.

If it has been wet, it will be buggered. Drying it out will rarely debugger it.

 

[Hussnainh8]

I don't fancy paying out £300 for a used SAM + god knows how much more to get it programmed for towing etc etc. I can live with the fuel gauge not working properly (will check fuel sensors in case) but the only solution I needed was for my towing trailer lights so I have decided to bite the bullet and get a bypass relay of eBay which will wire into the tail light and hopefully in theory power my trailer lights. Have heard that it can cause bulb issues etc doing it that way but the bypass relay says it's made to bypass the canbus etc so just going to have to give it a go. £30 compared to over £300.

 

[Hussnainh8]

7 Way Electronic Bypass Relay for 12V Towing Electrics - TEB7AS relay 5013008138779 | eBay

TEB7AS relay complete with Provides a safe connection for 12V trailer lighting circuits for use where the direct connection of towing electrics to vehicles may affect modulated lighting supplies, bulb failure monitoring, multiplex wiring, or other electronic systems.

www.ebay.co.uk

This is what I bought so in theory i don't need to use the SAM for the trailer as I can get the power from a tail light. Fingers crossed it doesn't cause bulb messages and play up etc which is my only worry.