Where are battery jumping posts

[Amg]

I have a 2020 Interstate Lounge EXT on a Mercedes 3500 chassis. I had previously a 2016 model. I can find the positive post in the engine compartment but cannot find a negative post. I can’t believe they would expect someone to randomly attach to a part of the engine or chassis to ground. I called Mercedes Corporate and they were of no help. My dealer is a far distance away and unavailable to call. Would appreciate some help. Thanks

[Pahaska]

Use any substantial metal piece in the engine compartment for the ground. Always hook up the ground last and remove it first.

[OTRA15]

What does your owner's manual say about jump-starting the vehicle?

For our Ford Transit van, we do what John just said FWIW. Pretty sure the owner's manual is fairly clear about this.

Peter

[Amg]

Not looking to jump start vehicle but connect a portable air compressor for power. On my 2017 there was a negative post. There must be one on my new unit just can’t find it

[OTRA15]

The Mercedes manual [not AS] should refer to the negative post issue in a discussion of jump starting the vehicle.



Please check that Mercedes manual without over-thinking this IMO. A lot of newer vehicles do not have a negative post per se.

Peter

PS -- FWIW a 2017 video . . . guessing that your 2020 negative connection is more subtle than this IMO:

https://www.youtube.com/watch?v=Z13_A_gwjkw

[Amg]

I checked the manual and even called Mercedes corporate in Georgia. They could not find it in manual and told me to go to the service department of a dealer. I am going to look around the engine compartment some more. Must be there

[OTRA15]

Thanks for the update. So you don't have that brass fitting sticking out for the negative shown in that YouTube video?

Here is another but for a 2016. Shocking that Mercedes could not help you IMO! We hook up our 12-volt compressor the same way John said in his earlier post, clipping the negative to the nearest substantial metalwork.

If the compressor runs, that is your "full scale model" confirmation IMO.



Good luck,

Peter

https://www.youtube.com/watch?v=JvWa4_gSMQg

[Boxster1971]

Originally Posted by Amg

I checked the manual and even called Mercedes corporate in Georgia. They could not find it in manual and told me to go to the service department of a dealer. I am going to look around the engine compartment some more. Must be there

Yes it should be there in same spot on driver side of engine compartment. I found the linked YouTube video that shows the engine compartment details at 13:30. Also in the attached image from this video you can see the brass ground stud on the driver side that I circled in red.

https://youtu.be/qYkWqVR9iGk

If you happen to have the optional Auxiliary battery in the engine compartment in this location it may obstruct the ground stud. If you do have the auxiliary battery just connect to the negative terminal as the van batteries have a common ground.

Hope this helps,

[Amg]

Thanks OTRA15 for you Tube video. I found brass fitting in the far drivers side of the engine compartment. It was not in plain site nor marked to indicate it was a negative post. The video showed me what to look for. Thanks again

[Boxster1971]

Originally Posted by Amg

Thanks OTRA15 for you Tube video. I found brass fitting in the far drivers side of the engine compartment. It was not in plain site nor marked to indicate it was a negative post. The video showed me what to look for. Thanks again

Glad you found it. That video and image I posted above was a 4-cylinder gas engine Sprinter so it didn't look right. Found a 2019 V-6 diesel engine compartment video (at 1:27) and image that also shows the brass ground stud in same location; that I annotated by yellow arrow. They have never been marked.

https://youtu.be/vqqkad9I3tw

[OTRA15]

Originally Posted by Amg

Thanks OTRA15 for you Tube video. I found brass fitting in the far drivers side of the engine compartment. It was not in plain site nor marked to indicate it was a negative post. The video showed me what to look for. Thanks again

Glad you found it. It might be instructive to look at the Mercedes Sprinter manual again, now that you do know where the negative post is, to see if the manual refers to it in any way, however obliquely. There should be some reference to it, in the section on jump-starting due to a dead battery, even if the language is poorly written or inaccurate.

Worth a final check, as a re-assessment of the thinking process here IMO.



As we say in the construction trades, "measure twice, cut once . . . "

Happy trails!

Peter

[Russ Abbey]

Basic electricity is, you have to have a ground or negative and a positive terminal. Also since the battery is grounded to both the frame (most of the time) and the engine you just have to put your ground terminal of the compressor to any heavy metal. It'll work as radio tech do it all of the time to mount radios in police, fire, rescue, and ham radio buffs to boot. Or at least they should be.
Good luck with your project, ours are at a stand still for now.

73
Russ

[Life is a Highway]

Always a safe practice and with a computer controlled vehicle mandatory. Make and break on the negative side not positive. Why? Induction damage to sensitive electronics and the change of blowing off the airbags!

Originally Posted by Pahaska

Use any substantial metal piece in the engine compartment for the ground. Always hook up the ground last and remove it first.