royamg

Hello everyone, I have a 2003 s55 that i recently purchased. it drove great for the first couple 100 miles but recently it’s been having a electrical issue. As i’m driving the dash will give out a red message saying check battery and all the lights get dim. moments later the ac will turn off, the windows won’t be operable, the radio turns off and whatever gear i am in at that time i am stuck in. within a minute it usually goes back to normal but it is very annoying and honestly quite dangerous. if anybody knows what the solution is or what it could be related to i’d greatly appreciate the help.

Astro14

I would start by checking the charging voltage from the alternator, and then I would check the battery itself. This car doesn't like weak batteries, and I would go with an AGM, as originally fitted, not a regular lead-acid, battery.

royamg

thank you for your help, i got the battery checked at oreily but i’m just going to replace the battery and see if it fixes the problem as well with my keyless go.

tusabes

No .
you need to do exactly what was said - check charging voltage while car is running and showing the error . It sounds like your alternator brushes are worn and once the alternator stops charging the warning lights come on and everything shuts down

it could also be a loose belt but that’s less common

royamg

okay thank you. how exactly would i check the charging voltage? i’m not very familiar with the electrical portion of working on cars

tusabes

The auto parts store has a tester they can use on your car. They need to test it when the error is occurring

royamg

Sorry i’m a couple months late to replying on what fixed it. You were correct about the alternator being bad. Took about 4 hours to replace it.

SilberGrau57

RED battery light is Alternator, AMBER battery light is battery charge low