W164 ML Bootlid and rear o/s door playing up

[Felix66]

Hi everyone!

Having a little(?) problem at the moment.

For around 2 days boot lid on my ML 320cdi(2006) wouldn't open. All the doors opened and closed fine, except boot lid.
Then, today, the rear o/s door's lock got stuck too. Again, other 3 doors were fine. I could only open it manually, once inside the car.

My first thought/plan of action was to somehow climb into the boot via rear seats, open it manually and then check the fuses.
Went to the car, unlocked it and, surprisingly, suddenly everything worked ok again, boot lid, rear doors etc.

Scratching my head in disbelief, I opened the fuse diagram to see if there is maybe a corresponding fuse..... Sure enough, not a mention of any of those except "Remote tailgate closing" which my car doesn't have.

Being a bit of a Frank Spencer with two left hands and fairly clueless about cars, I finally realised that maybe there is no such thing as fuses for boot lid and rear doors

My desperate guess is the battery(which one - there are at least 2??) must be on the way out and is playing up with electrics.

Not sure how to go about it ie. how do you check if your battery is empty(??) or perhaps insufficiently charged, maybe even dangerously old?

I tried looking through the owner's manual but not even a suggestion as to what battery is inside nor what the replacement one should be. Just the usual - visit your nearest MB workshop blah blah..

Shops(Halfords, ECP etc) mainly suggest a very specialist battery(AGM or something like that) which, as I understand it, is recommended for newer vehicles with stop/start function.
Those batteries are very expensive, and my car doesn't even have stop/start, so I thought it would be an overkill to get those. But if not one of those, then which one?

Please suggest any ideas as to what could be wrong with by boot/door locks playing up, as well as how to check the battery's "level"(if that is at all possible??), and where to get a new one if mine is not good enough.. Well, to get a new one, I should first know what make and model to look for, so if you have any idea, please help - I could do without a "visit to my nearest MB workshop.."

Any input will be greatly appreciated!!

Sorry for the long essay!

Cheers

 

[AndrewOl]

Hi Felix, any auto centre will be able to test your battery. Usual sign of impending failure is poor starting or flat battery though. The rear door latch is electric but may not have a dedicated fuse. So this could be acting up. My 2006 GL has a never ending series of electrical gremlins one of which is the auto rear door sometimes working sometimes not. The central locking also occasionally unlocks while driving which scares the bejesus out of everyone in the car! In desperation I changed the main battery. £177 from main dealer, made no difference but I made sure I had a cup of coffee while I waited so I’m happy with that. These cars are getting on and are fairly complex so I’m getting used to the idea of it having some fault or other. Most come and go until it is properly broken, least you can usually fix it then!

 

[richard]

Please get the correct battery. AGM batteries charge differently to Standard batteries, so the car has to have the correct kind.

This could be a battery, or it could be the rear SAM failing which controls it.

Battery is under the right front seat - you can slide seat forward, remove the plastic cover which expose the negative terminal, which may have a date code on it (week number, year number) so you can see how old it is.

Cheers
Richard

 

[Felix66]

Hi Andrew,
thank you very much for the message, t is always nice to hear from someone who has similar car since they share fairly similar gremlins.
I have been very lucky so far, bought the car year and a half ago with just over 100K on the clock and haven't had any major trouble with it(touch wood!)
I am useless at car diy so just as well
The car has a little leak at the bottom of the engine but I have been advised to leave it until it gets much worse-the leak is so small that the car only lost something like 1/2 litre of oil over 10K. Apparently it is a very well recorded/known problem with the oil cooler gasket on 320 Cdi's.. Do you happen to know if 420 has the similar problem? When the time comes(hopefully I will still own the car) the repair will take a whole day and a new oil cooler but what the hell, it's worth it, the engines are supposed to be bomb proof and the gearbox feels pretty good too.

I spent good few hours searching the net for the fuse box diagram and then trying to make sense of it(couldn't find mine, it is incredibly well hidden in the space under the spare tyre!) trying to find out where the hell is my boot lid fuse positioned. When I finally realised that there isn't one, I then spent another few hours chasing some info on the compatible batteries. Out of interest which battery did you go for, so-called AGM or the regular one, (whatever "regular" means), £177 from main dealer sounds pretty good!!

Yes, having had a little think about it all, and considering that car starts like new, each and every time, chances are the battery must be ok, it is the electrics that were just playing up a bit.. Hopefully it was just one off. Trouble is, with those electrical glitches, you start to lose the confidence in your car and start subconsciously praying each time you press the remote

Cheers!

 

[Felix66]

Please get the correct battery. AGM batteries charge differently to Standard batteries, so the car has to have the correct kind.

This could be a battery, or it could be the rear SAM failing which controls it.

Battery is under the right front seat - you can slide seat forward, remove the plastic cover which expose the negative terminal, which may have a date code on it (week number, year number) so you can see how old it is.

Cheers
Richard

Thanks very much for the advice Richard, muchos appreciated!

I will have to have a look at the battery and try to establish what type it is, for the reference if nothing else..
If I am lucky to see the date, how old is old, in the world of batteries?

Also, what is "SAM" controller and what does it look like(big or small)?
Where is it usually positioned and how can you tell if it is faulty?
Chances are, I won't be able to tell anyway, jump starting the car is just about all I know about car electrics

Cheers!

 

[AndrewOl]

The SAM is part of the car control system. It is under the rear fuse box and is just a little black box with connectors on it. Worth looking for any signs of water ingress in this area as it’s a known problem area for the ml. I wouldn’t worry too much about a small leak. The GL uses that much and is pretty dry underneath. I’m two years into my first MB and have found lots of other more pressing things to spend my cash on! Lovely car but a pita sometimes. I would ask around for a good Indy MB garage near you. They have the kit to diagnose these surprisingly complex cars.

 

[Felix66]

Thanks Andrew, will have a look at the SAM, hope not to find any water in there
Car has been fine last couple of days so with a bit of luck that was just a one off, fingers crossed..

Cheers