edpare

I ran our ‘20 GLC300 through a car wash yesterday for the 50th time since new. The headlights were set to Auto and turned on inside the car wash as usual. When we emerged, the lights did not turn off, and stayed on for the 30 minutes it took to drive home and shut the car off. Never happened before. Lights behaved normally in subsequent operations.
Does anyone know where the external ambient light sensor is? Something new happened in the carwash.

chillysyrup

on the dash I think or behind the mirror

bishop64

The light sensor is behind the rear view mirror/overhead console and the windshield.

In this video, it is the same as the rain sensor.

edpare

Thanks bishop64! Unfortunately for me, there was no obstruction there, now I assume the worst.

eddieo45

how many miles on it Ed?

edpare

37000 miles. Windshield replaced last December by dealer.

eddieo45

so, you're still under warranty; no worries!

mikapen

What's your battery status?

edpare

I assume it’s OK; it usually settles down from 14.9 to 13V after 15 minutes of 55+ mph. When demand is higher like seat heaters on, or A/C on max, or more driving to urban stores, it may not fully recover until I get sufficient highway miles. I’m retired, so I cheat (of course) and use a CTEK if it stays at 14.9V longer than a few trips. We don’t go out every day.

mikapen

Good practice, probably eliminating Low Battery as the culprit.
Good luck.