Just to confirm the X166 GL takes a H8 battery and not a H9?

 

I just replaced the battery in my 2015 GL350 this morning. Bought the battery DURACELL from Sams Club on sale for $159. I could not start the car with the old battery (it was totally dead) to drive it to Sams unless I called AAA etc. So I decided to do it myself. Used another battery which I connected to the battery posts under the hood and was then able to move the front passenger seat forward. Once the seat is moved up and forward you can then see the plastic panel under the seat. The plastic cover is pulled off and then to get the vent panel off you have to lift a small round plastic clip with a flat screwdriver. It pops off easily. Once its off, pull slightly to the right and the vent panel comes off. The other cover panel below the vent panel has two clips at the rear (by the rear seat) and are pushed in and it then lifts off and is pulled towards you and is then off. The battery is then clearly visible.

I unbolted the negative terminal first (10 mm) followed by the positive terminal. Then I removed the 2 hold down plate nuts (13 mm) and the chassis ground cable to give me more room to slide the battery to the rear. Also I removed the vent pipe from the battery. My carpet had already been cut previously so I did not have to do that.

The hardest part was trying to lift the battery out of its well. After a lot of wriggling I was able to lift the rear end up first to about a 45 degree angle and then pull it out. I was going to place a loop lift strip under the battery for the next time as it would make it easier to lift but I forgot when inserting the new battery in. Anyway, i plugged the opposite vent hole of the new battery and it was a lot easier shoveling the new battery in the well than taking it out. Reconnected the positive and negative terminals as well as the ground chassis cable, the vent pipe and the tie down plate/nuts. All electrics came back on and the clock was off for a couple of minutes and it reset itself. The only reset I had to do was the side mirrors would not fold in when locking the car. This got reset by navigating the assist feature on the cluster from the steering wheel controls and first disabling it and then re-enabling it. Car started up just fine.

The only thing that bothers me is that the old battery was an MB battery that had been replaced by the dealer as part of its CPO program when I bought the car and the battery was under 2 years old (about 22 months) and I had put about 7000 miles since it was replaced. Will see how long this one lasts. The dealer would not replace it under warranty because it was paid for by MB and not me. If I had paid for it it would be covered.

When I mentioned earlier that the battery was dead, there was no warning that i would expect to see from other batteries that are dying. It worked perfectly 2 days ago when the car was last driven, nothing was left on, and when my wife went to start it, with the keyless go, it unlocked the doors and when she went to press the start button - nothing it was totally dead and would not even accept a charge from my CTEK 7002 charger.

 

For $50 more MB roadside would have done it for you.

 

Can you or anyone verify that the cord "yellow circled in photo" does not need to be detached before pulling this second vent panel up and towards me? any other notes, suggestions, thoughts. Many Thanks.

 

I disconnected last time I changed the battery.

 

@BlownV8 ... excuse my paranoia as these plastic parts can be brittle and fragile, but do you recall how you disconnected it, just pull up? thanks

 

I don't recall but you may want to use a small mirror and look underneath to see and how it attaches to the cover

 

All,
i have an issue that is urgent, i am hoping someone here can help. I replaced my battery and followed the instuctions with the key, except that the car car clicks and doesnt start. Does anyone know what the issue is?

 

Dead battery or loose battery connector. Try to check connectors first and charge battery

 

Original OEM battery finally wouldn't put out enough power to start the truck after 7.5 years. Took it to Pep Boys and they installed 900 CCA AGM battery for $207 including tax and installation. 48 month warranty. Surprisingly, it was done in less than 30 minutes and the mechanic didn't even have to cut the carpet.

I had called Sams Club, but they said that they cannot install batteries unless they are under the hood or in the trunk with easy access.

 

You should look into replacing the secondary small battery in the back. It's likely at the end of its life also.

Jeff

 

Batteries plus, has the secondary battery for $23.
Duracell 12-1.3F.

easy install

 

Replaced mine today from Pep Boys, $165. If you have a 10mm and 13mm with long extensions, a flat head and a razor, its a 15 minute job. I spent more time getting tools out of the basement. Lost one of my 13mm sockets. The wanted another $70 to install because it was "complicated".

The battery was tricky to get out and it would have been easier to cut the carpet more if you are not strong enough to pull it out at an angle.