Mr. Lin

Hello all, got the fabulous red battery light on the dash this evening while out to dinner. Car continued to drive fine, however there were some odd symptoms I was hoping someone may be able to explain before I take it to the dealership on Monday. The A/C, despite being on MAX, would not blow at the velocity it had in the past, the radio turned off while driving and the command system was unresponsive. Has anyone dealt with this problem in the past?

QWKSNKE

Sounds like it was cutting out the accessories because of your battery issue

Tlnt60

It could be the alternator as well. Easiest test would be done by doing a load test at a local CSK or Autozone type of place. I would start there. Also, depending on where you live weather plays a factor if you have a water battery. If you in fact do - open the caps on the battery and ensure that there is water covering all the led cells.

ahgli

I had the exact same symptoms not too long ago, ended up being the water pump, it caused failure along the belt drive. I replaced the alternator, battery, all pulleys and water pump. I did a load test also before replacing everything and it showed that the alternator was charging properly so don't rely on the test too much. Check for leaks around the water pump and go from there.

Hope this helps

604 C63

My money is on the battery, esp if it is original. When those AGM batteries go it is sudden,
and next thing you know if you try to blast the AC it aint nothin but a whisper in your ear
and you can't run other stuff either. I could have used a sundial to time my windows going up.

Mr. Lin

I checked for leaks around the water pump and didn't see any leaks. that would also drop the level in my reservoir, wouldn't it? I'll try testing the battery. is it as simple as taking a voltmeter to the terminals?

ahgli

Yeah, it should read around 12v while the car is off and 14+ while the car is running.

Mr. Lin

12.2v off and 13.8v on. seems low, huh? also, I think I'm the 3rd owner, so I have no idea if this is the original battery. it's a 2008 with 71k miles and I live in Tucson, where it's been 105°+ quite often this year

Tlnt60

So being that you're a fellow Arizonian, I would say the weather is the issue. I believe if I remember correctly that you should be at 14.4 across with car on/running. 6 cells, 2.4 across each one. I'd start with the battery.

604 C63

It takes a lot of juice to run our cars, and once those batteries start to degrade.....
for me its a matter of city living, and lots of short hops that never allow much actual charging time.

And Tint60 is correct with 14.4.

Mr. Lin

Ok, I'll start there. I tried looking up the battery on parts.com and genuinemercedesparts, but they just say it's discontinued. Any luck with any particular brand/model? Thanks for the help and advice.

604 C63

Im in Canada, so I got a Canadian Tire replacement. Nothing saids it needs to be OEM.
Take a search there are a few threads here about different models.

realjones88

You can also try putting the battery on a trickle charger and see if you can get it back up into the proper range before you go out and buy a whole new battery. This is especially true if the car has been sitting or you don't do long drives.

Mr. Lin

went to get a new battery. car went into a nasty limp mode and then abs and esp were disabled on the dash. how about that for symptoms? car doesn't even want to go into reverse and didn't like when I gave it any gas

604 C63

Not enough power to run. Been there, done that.

Mr. Lin

Replaced the battery. Battery was seemingly original, 1508 engraved on the neg terminal. Drove around the neighborhood, similar symptoms, just not to the point of limp mode, indicator came back and all. Thinking maybe the alternator isn't charging the battery and the car knows it. Hoping it isn't the water pump, although the car has been running 4° warmer since the first warning indicator, up to 212°/199° Oil/Coolant

Tlnt60

Next up would be voltage regulator.... Have you tried Indy shop or dealer, might not want to cause other damage.

Tlnt60

Need to measure voltage with car running to make sure alternator is working

Mr. Lin

on the old battery it was 13.8v, I can check the new one tomorrow morning

Tlnt60

Right so with the new new battery you're still having issues correct?

Mr. Lin

That is correct. As soon as the indicator came back on, I drove home before the radio had the chance to cut out and the car go into limp mode

Tlnt60

Do you have a way to measure voltage with car running?

ahgli

Im betting it's your alternator

Tlnt60

Yea it's looking like its his alternator, I think we were all hoping it wasn't, and was just a battery.

ahgli

Did you check your accessory belt? The Dubai heat is what stretched mine causing a domino effect and taking out the water pump and alternator.