pm93

Hi All,

Car is a 2005 C230 Kompressor. I've had the Battery/Alternator Malfunction message come up for me after start up for many months. First thing I did was get a new battery as the old one was probably still the original it came with. No luck with that so I observed the voltage was often times low ~12.5 volts and intermittently actually charging the battery. Changed the voltage regulator in my valeo alternator and could see the brushes were well worn enough to be causing everything.

After changing the VR and wearing it in for several weeks, the light has continued to show during startup. Now the interesting thing is having the hidden menu up shows that the car always starts and runs at 12 volts UNTIL I spike the RPMs on the engine past 3k or so. Then it will be at a normal steady 14.2 volts for the rest of the time the car is on.

Any ideas what might be causing this? Ive been living with it for a while, cleared errors codes, reset computers, etc.
Thanks for reading

Plutoe

Sounds like you wasted your money on a battery and voltage regulator---then if your story is correct and you did not load test, the only thing left is a faulty alternator!

Preet

i believe the VR is the still the issue, where did you get the voltage regulator online or from the dealer?
i had the same issue with valeo that i bought online, the aftermarket VR are not programmed the same as what's sold by the dealer. i also had the same "runs at 12 volts UNTIL I spike the RPMs on the engine past 3k or so"

pm93

Hey Preet,

That sounds like a reasonable answer to this mystery. I did indeed buy it online from here:
Bummer that I will have to redo all that work with a dealer bought part at some time in the future. Atleast it's a problem I can live with until I feel up to the task. Thanks for your valuable insight! Have a great day

Preet

i believe that is the issue as well