aboling

I have an 03 SL 500. I had it 3 months and thought I needed to change the voltage regulator. I changed it and now Im having all kinds of issues. I replaced the two batteries and also a new alternator and my warning light went off but the next day I drove it she reappeared. Not sure what else to do or why the light came back on. Is there something I need to reset. Very confused!!

moretech

In this case you'd best get a good scan done and check for trouble codes before doing anything else. This car is hard to figure out electrical problems without proper diagnostics from a scanner that can do Mercedes codes.

moretech

aboling

Would my check engine light be on? Mine is off

moretech

I'd say "NO" to that. That checks for misfires etc: Could be the battery splitter in the trunk. It "splits" power between the 2 batts. A box like object which allows the alternator to charge both batteries. Charges front batt 1st then rear. See if you have a volt meter and it reads 14 volts on both batts. If one is much below 14v it could be that. It is expensive and can go bad. But do the scan ASAP and do not replace it without getting some codes read. May be something else that is cheaper. Maybe just a bad connection even. Always do scans before spending your $$ to try to determine a fault like this. Way too complex electrical. Once codes are read the forum can help analyze them and steer you to a solution. Many top notch fellows in here. Welcome to the forum. I'm not worth a thing working on my '03 without this place. Learned a ton load in here.

moretech

aboling

I think I will start with the scan. I didn't just replace think=gs. The batteries went dead (the starter battery was the original battery from when it was new) then I took the alternator off and had it checked and it was bad. Im looking forward to leaning a lot from this forum. Thank you!!!

Rudeney

Note that a generic OBDII scanner will do you no good diagnosing this issue. Those only scan for MIL (check engine light) causes. You need a scanner that reads proprietary MBZ systems. SDS (MBZ's Star Diagnosis) is best, but iCarsoft's i980 or MBII will work, too.