Hello,

started getting some random startup issues on my wife's 2008 R350. There's another post from me elsewhere that discusses the troubleshooting I went through, but suffice it to say December was not a great month for me.

Basically our 2008 R350 with 86K has started to exhibit quite a few issues which required the repair of the intake manifold to address fuel trim and stuck open errors from the ECU. I've done the repair which came down to the 'tumble flap actuator' which is typically made of plastic and I replaced it with a Dorman unit. Again, check my other post that discusses this issue.

Anyway, no sooner did I fix this issue did I get the dreaded, 'Don't change gear, Drive to workshop' beeping light which will not go away. This turned out to be the dreaded, 'Intelligent Servo Module', Hoehn MB please take 1100 from me that I have no use for

Anyway all of this didn't fix the random start problems I started to have so lo and behold I decide to replace the main battery and aux.

So, here's my advice to you. Do not attempt to do this job from behind the passenger seat. It doesn't work and if it does work for you, it's only because you took a utility knife and decided to shred the $$$$ out of the carpet.

Nope, for me, the easiest way to do this job is remove the front kick panel on the passenger side (extra points if you don't bust the plastic mounting clips), unscrew all 4 torx bolts holding down the front passenger seat (without unplugging the electricals) and carefully slide that back, remove the lower plastic seat trim, remove the side door trim and remove the carpet, insulation and fiberboard on the passenger side. Fiberboard can only be removed when you've removed approx 6 10mm bolts.

Once that's done, you'll have easy access to the aux battery and main battery.

Again, this is from the front of the passenger seat, not behind it. This method does the least amount of damage to your interior.

Oh, and don't forget to reattach the vent tube for the main battery.

Batteries Plus sells the Duracell for 150 right now and the aux for 20. I believe the AGM equivalent is $200.

Thanks

 

Thanks for the tip.
I guess that you have to slide the seat all the way back before you remove 4 bolts that hold the seat, right?

Last time I had the dealer and they charged me $300 for the main battery and $150 for the labor. I asked why so much for for the labor, the service advisor told me they have to take out the seat????.
I complained to the director of service that why not replace the aux as the same time or I will be charged the labor next time if I need to replace the aux battery. He said that if i need to replace the aux then the labor will be free next time.

 

Actually, just did it as well... and puling the seat bolts is good to make more room back there... but that is all I had to do. The carpet is scored so a solid pull while still attached under the trim is all it took. It created a nice hatch that folded back and looks fine back in place just like the OEM intended. Now it was a royal PIA to get it back together... but I did it.

I have also done the Aux battery and from my perspective the main battery is easier to get to from behind the seat than trying to move everything back and going in from the front.. but can also see how that can be done.

Also, you really need to make sure you put in a AGM... You do not want just a sealed lead acid battery in there.. you never know if you are going to be hit... and you do not want a lead acid battery bursting in the passenger compartment. The price difference of 40 to 50 is minimal compared to the safety. I picked up a AGM from Autozone for 190.00