Rear Window Defroster (LED Flashes...)
 

My rear defroster switch flashes sometimes for about 5 seconds, then the light will stay on as normal.

I know it does this because it uses a lot of power, and then it returns when power is available again.

But everything is fine! I even have a new (roughly 3 month old) Mercedes-Benz battery. I can leave the lights and radio on for hours, and the car will still start. The battery and charging system are fine.

I know this is nothing to worry about, and probably a pointless post.

But.............. any thoughts?

Does this happen at or near idle? If so, perhaps your alternator is telling you it's tired...

Follow Up...
 

Well, the solution just occurred to me a few days ago.
Firstly, I still occasionally get the flashing rear defrost light, but the charging system was perfect otherwise.

Well my blinkers are irratic (hazards too), my intermittent wiper work 5% of the time, and my rear defrost gets low voltage....
The connection??

It's all in that one combo relay!

Part No. 000-821-08-63 is selling for only $41.77 in Fastlane! I'll be ordering that now.

;)