rmalford

Hello this is my first post and I own a 2007 c230 sport black w/ grey interior. I'd like to post a problem with my vehicle and try and acquire some answers that will help me solve the issue at hand. Hopefully, I will be forgiven if this is in the incorrect forum section or maybe an admin will help me out by moving this thread into the right spot. I haven't owned this car 6 months and about a month ago I started receiving the big red picture of a battery on my instrument cluster intermittently. I have been lazy and not looked into it. I also just moved up from Houston and started a new job this month so that may have played some part. I was driving in the light rain today and was running all types of loads: windows, sunroof, a/c, wipers, radio, fog lights and while I was in the bank drive thru today when I felt a surge of power loss. Motor did not die. But, I was now in what I would think is safe mode. My ABS light was now on and on my instrument cluster it put out a message saying that my ESP, ABS and some other electronics were disabled. The a/c blower motor wasn't putting out any air in any setting, the radio wouldn't turn on, and sunroof wouldn't work. I couldn't get out of which ever low gear I was in. This is why I was thinking I was in a sort of safe mode. I stopped at the local part shop and turned off the motor and it wouldnt start and I put a meter across my battery. 10 volts so I blindly put in another battery. Car starts up and battery light is back on in a few seconds but all electronics now work so I rush to my destination. Curious I put the meter across the battery and it reads 12.1 volts. Start it and with the meter on and motor running it is 11.9 volts. Motor off again and its 12.10 volts. Motor on 11.9 sometimes 11.8. After I left the parts store I've driven it about 45 miles with a few stops in-between. Alternator? Voltage Regulator? Belt? I haven't checked these out. My sunroof is the only thing still acting screwy. The switch for tilt roof close makes it open instead of close. Anyone with similar issues or advice? Thanks a lot in advance.


Robert

SunnyRayToronto

battery should be changed every 5 years - yours is 2007 so it's about 6 yrs old. Check date stamp on -ve terminal of original battery. Which battery did you get? OEM?

read owner's manual (or stickie at top of forum) - need to resynch sunroof - esp - power seats - HVAC - etc,...

Go into "dyno mode" to watch voltage - search for procedure
search "limp mode transmission"

rmalford

SunnyRayToronto, I appreciate the help and your reply. I swapped out the old battery today for a new Duralast Gold (I know). Original OEM was the previous battery. I agree the sunroof might need to be resynched. Everything else is working fine at the moment with the exception that I have low voltage at the battery terminals with the motor running (11.9 volts). I'm looking for a higher reading. I'll continue my search.

SunnyRayToronto

OEM has 100Ah,... sometimes fussy

Anyways, your problem sounds like a weak alternator

voltage should be about 13.6V at idle and about 14.2V at 2000RPM

mileage?

rmalford

Thank you. Weak alternator is what I was guessing without bench test. 84k miles. I had my leads on the batt terminals while someone took it up to 2000rpm with no change in voltage. Steady at 11.9.