[FLHeat]

I have noticed for a while now that my start function has been acting weird. When I do my routine to start the car break, press button etc, everything turns on and the needles in the speedometer and tachometer move from zero to the other end but the engine won't start. So I take my finger off the button and foot off the break and do it a second time, recently even a third time and then it starts normally.

Any idea what could be happening here? Thank you in advance for any assistance on the issue.

Jay

 

[jbanks15]

my 2 cents.. how old is car battery?

 

[FLHeat]

my 2 cents.. how old is car battery?

I don't know, it came with the car when I bought it a year ago. I had thought about this, it's great that I am getting confirmation on my suspicions. I understand that this car has two batteries? Should I change both? or the main one. Any recommendation as to brand from experience? Also is there a diagram, I am not that familiar but would try to switch myself. Thank you for your help.

 

[jbanks15]

just the main one should do it... r172 owners will jump in

get it comprehensively tested at autozone, etc for free

is there a date sticker on it?

 

[jbanks15]

battery recommendations

site:slkworld.com battery recommendations - Google Search

 

[jbanks15]

battery change

site:slkworld.com r172 change battery - Google Search

 

[jbanks15]

your title says start stop... so that would yes be the auxillary battery

see links above

also

https://www.youtube.com/results?search_query=mercedes+slk+r172+change+battery

 

[jbanks15]

 

[jbanks15]

Replacing R172 Aux/ECO Battery to get Start/Stop working

T AFIK, if the battery levels are too low or borderline when the AC is turned on, then the AC demand trumps the ECO stop start until the battery charge reaches a suitable level. I doubt it has anything to do with cabin moisture levels as such. That would intuitively make more sense ?

www.slkworld.com

 

[FLHeat]

just the main one should do it... r172 owners will jump in

get it comprehensively tested at autozone, etc for free

is there a date sticker on it?

will look for the sticker and get tested. Great advice. Thank you

 

[Poulsbobill]

I believe unless you have ECO you only have one battery. Does the R172 have one or two batteries?

Bill

 

[Sootsoot]

The 172 has two. The auxiliary is behind the left seat (behind the netting)

 

[Poulsbobill]

Since i had read that w/o ECO there is no 2nd battery and my car doesn't have ECO, I had to check.

I can verify that a 2015 w/o Eco has no battery. I have a compartment but no cables nor a battery.

Bill

 

[Sootsoot]

Makes sense. Never seen a 2015 without ECO in the UK?