Fury1705

My car had this malfunction yesterday while I was driving. My car its an e240 w211. The car started and drive fine but after 30 minutes or so driving this malfunction comes on but after turning it off for a couple of hours the malfunction would be gone and it would show again after 30 minutes of driving. Does anyone have any idea ? Is it the battery that has hone bad or the alternator ?

Heguli

Well, it's really hard to say over the interwebs which or what is broken. If you have a multimeter, measure the voltage from the battery posts, engine running around 14 volts and after the while engine has been shut down, 12,7 volts would be good. And even if the battery voltage is good, you should get the battery tested. Both batteries, rear main battery and front auxiliary battery if so equipped.

rapidoxidation

I wonder if the brushes on your alternator are done.
Check the batteries as stated, and monitor the voltage as you're driving.

CaliBenzDriver

Voltage goes nuts reliably after 30mn driving.

It sure sounds like your chassis is equipped with a "smart alternator" remotely controlled by the ECU.

​​​​​​Monitor your chassis voltage while driving before rushing to conclude it's a bad alternator. Likely is the ECU 🙂

ot1

1. Is this the RED warning display you are referring to?
2. What year is your car?
3. You you have SBC braking? If so how old is the AUX battery?
If you don’t have a voltmeter you need get one. Lowes, Home Depot, Menards, Amazon about $40