Which fix works for you?

[LVSteve]

Leaving a Christmas party last night, my Mercedes ML flashed a message "Auxiliary Battery Malfunction". Didn't even know I had one. Seems it is a small battery to maintain a smooth voltage to certain key electronic bits, one of them being the transmission.

Much Internet research later enabled me to locate the battery in my car. It has changed at various times in the history of the ML, and there are two possible types . Youtube also showed me various ways to change the battery.

Method 1 involved removing some trim in the luggage area and pulling some other trim to gain access. Method 2 involved dismantling almost everything in the luggage area to gain access. See the first video. Method 3 requires two moves with a sharp knife. See second video.

So what would you do? See above poll

Method 2 video.

[ame]https://www.youtube.com/watch?v=A9XaApSoAAw[/ame]

Method 3 video.

[ame]https://www.youtube.com/watch?v=ATjTFgx2Yzs[/ame]

 

[soFlaNative]

Trade it in.

 

[LVSteve]

Trade it in.

Can't do that, the ashtrays aren't full yet.

 

[CH4]

I've been lucky and able to look up the code and fix things myself. Usually a O2 sensor, one time a cam position sensor.

 

[kev74]

If you think you can do it the right way, do it.

Its too nice of a vehicle to start slicing and dicing.

 

[LoboGunLeather]

As the old saying goes, if you have to ask what it costs you really cannot afford it.

The decision to purchase a Mercedes Benz automobile included a decision to accept periodic financial beatings.

 

[Ματθιας]

I didn't do the poll as there wasn't enough info.

The way I see it:

If you're going to keep the vehicle long term, do it the slow, methodical way.

If you're going to sell it fairly soon, slice and dice.

 

[ladder13]

Don't Bubba the Benz.

 

[Old 44 Guy]

My son in law owned a body shop for 42 years. When a Mercedes came in for a bid he doubled it. Half the time he got the bid anyway. Lousy parts replacement system. And an over engineered auto.

 

[Onomea]

I voted cut carpet. That's a crazy amount of work to replace the "auxiliary battery" by taking everything apart to gain access. And from the video, with the cut carpet approach, the cuts are not very noticeable.

The Germans build nice cars, but that's a bad design.

 

[rwsmith]

It's a toss-up.....

In past days I would dismantle everything.

Nowadays it's more 'run to the dealer'.

 

[LVSteve]

I voted cut carpet. That's a crazy amount of work to replace the "auxiliary battery" by taking everything apart to gain access. And from the video, with the cut carpet approach, the cuts are not very noticeable.

The Germans build nice cars, but that's a bad design.

If you think that's bad, on the earlier ML's, say 2010, the auxiliary battery was behind the main battery...in a pit underneath the front passenger seat. No amount of carpet cutting can fix that one.

 

[Grayfox]

Sometimes trying to save a few bucks just ain't worth the trouble and aggravation. I've only worked on a couple of Mercedes in my time and I regretted it every time.
Just because you got a message that the auxiliary battery was malfunctioning,doesn't necessarily mean the battery itself is bad. Take it to the dealer, have them check it out and pay the bill. It'll be well worth it. Trust me on this.

 

[TLflag]

Car

Wait till you try and buy the new battery. They will only sell

parts to their dealers here, I tried.

Wish You Luck Terry

 

[glenwolde]

As the old saying goes, if you have to ask what it costs you really cannot afford it.

The decision to purchase a Mercedes Benz automobile included a decision to accept periodic financial beatings.

...and the beatings will continue until morale improves...

 

[LVSteve]

Sometimes trying to save a few bucks just ain't worth the trouble and aggravation. I've only worked on a couple of Mercedes in my time and I regretted it every time.
Just because you got a message that the auxiliary battery was malfunctioning,doesn't necessarily mean the battery itself is bad. Take it to the dealer, have them check it out and pay the bill. It'll be well worth it. Trust me on this.

That's a good thought, but further research shows that these batteries are a "use item". Some say they don't last more than four years. The car came with VERY low mileage for a 2014 when I got it late 2019. Then there was COVID, and after that I've had extensive periods of working from home. I suspect this is battery #2, but it could be the original.

Yes, the auxiliary battery relay is another possibility. However, popular advice is that if your battery is more than four years old, get a new one, so a new battery is in my future, regardless of who does the work.

 

[Bald1]

As the old saying goes, if you have to ask what it costs you really cannot afford it.

The decision to purchase a Mercedes Benz automobile included a decision to accept periodic financial beatings.

I hate. I mean really really hate that old saying. It's dumb!!!!! It's not about being able to afford it. It's wether or not you want to spend your money on it. Is it a worthwhile purchase/investment. It's called being smart/frugal. And those are usually the people that can afford whatever they want.

 

[ACORN]

Wait till you try and buy the new battery. They will only sell

parts to their dealers here, I tried.

Wish You Luck Terry

Many of these batteries are sold aftermarket. Before everyone starts with "only OEM", know that Deka/East Penn Batteries, makes and labels batteries for many car manufacturers, such as BMW and Freightliner. Part numbers on auxiliary batteries are like AUX12, AUX14.

 

[raljr1]

Reminds me of the time I spent two days on my back under the car, and three trips back to the pipe bending shop to get the correct bend, to save $20 on the installation charge for an exhaust pipe from the manifold to the muffler. Take it to the shop and skip a couple dinner out.

 

[ACORN]

IDK what year you have but a 2015 ML350 auxiliary battery is a AUX14. $125 at NAPA.
I shudder think what the dealer would want.