stevemos

2014 C300. Battery not very old. It does not seem to get fully charged while driving and after a while the car will not start unless jumped. (And then battery needs charged a little to keep electronics running smooth)

it takes like 15-30 min to charge battery to full charge. Then after a few days of driving2-3 hrs/day start getting warnings for everything (On dash) then car will not start, like battery is just below min voltage & electronis wont let it attempt to start. I Connect to a little trickle charger for 1 min and it starts fine. Leave charger on battery over night and good for a few days.

read some comments about battery relay charge module?? (That electronics run on smaller separate battery) It does seem like something is preventing alternator from charging completely. But When I go to order the Battery Module part, it says it does Not fit my vehicle.??

does my W204 Not have this?

any suggestions?

thank you

NZ-Merc

Hi I have a Ctek battery charger and would highly recommend one and suspect your charger may not be fully charging it correctly and this would be best place to first start.

C300CA

Me too have a Ctek trickle charger charging the battery whenever I like to. The first factory battery only lasted three year. I am on the second just passed three years. Since I drive it much less nowadays, a few times battery discharged below minimum and all kinds of warning lights came on such as ABS not functioning or some bulb burnt etc.

When starting, starter cranks noticeably slower than my other cars and it has been like this since brand new. I guess it is the design. The battery ground cable is rather long so it has more voltage drop than short cable. I thought about shortening it but never wanted to do it.

C300CA

Corrections: First battery lasted five years. Second battery just passed five years...

stevemos

I found the AUX Battery, it is original 7 yrs so I am going to replace that first.

stevemos

Replaced battery, and seems to be fixed.

stevemos

Well,,,,,, not exactly.☹️

Everything was working fine for a couple weeks, now it is dead in driveway. Not batteries, both are charged but it will not start.

fob opens doors

dash comes on and radio works.

No start, no click. Batteries fully charged.
tried jumping, no crank. No click

(Dash would go dim then back on - not while I was tying to crank)

Any ideas?

NZ-Merc

Hi,
My Starter motor just completely died at 125,000KM no warnings, turn the key dash lights up no noise at all from the starter.

I removed the lower splash guards and connected test lightt to the small starter wire, while turning the key to start the test light powered up showing the solenoid wire was powered up as it should be but the starter did not crank.

New starter installed and started straight up.

Not sure about your dash lights only thing you may have had headlight switch in auto and lights turned on?