Q: Low voltage radio error

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My 2007 slk350 has a radio that has stopped working. When I turn on the car it plays for 15 seconds and then shows "low voltage" on screen and turns off. It has a brand new battery so I know that isn't the issue.

My car has 120000 miles.
My car has an automatic transmission.

Hi there. Check the battery cables for any corrosion. If there is corrosion, then clean the battery posts with baking soda and water mixed. Then check the voltage on the battery. If the voltage is 12.6 to 12.4, then the battery is okay.

After testing the battery, check the alternator for voltage when the engine is running. The voltage should be 13.5 to 14.7 volts. To check the amperage on the alternator, turn on the high beams and roll all the windows down all at the same time. If the engine bogs down or if the lights dim as the windows are activated, then the alternator is not as effective as it should be. Keep in mind that just because a battery or alternator looks good does not mean that it is good. If you need further assistance troubleshooting your low voltage issue, then have a local expert, like one from YourMechanic, diagnose the electrical problem and pinpoint the proper repairs.

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