Ok, heres the deal, really strange. About 2 weeks ago I got into my 05 C230k and got the message in the subject line.
Right signal on the dash blinked really fast and the light in the mirror did not work. This went on for a few days and
then all went back to normal. This just lasted a few days also. NOW, I get the onboard message but the signal works
fine and the indicator on the dash clicks normal. The error message appears from time to time but seems to clear it
self for no reason. The whole time the signal light and dash indicator works fine. What up with this ?

 

I had exactly the same problem, on my '07, except with the left-side mirror. It started as I was driving away from the dealership after an unrelated minor repair! Maybe when they washed the car they got some water behind the mirror. Anyway, it came and went for a few days, then before I had a chance to take it back to the dealer it fixed itself.

HS

 

Thanks for the response. Glad to know I'm not the only one with this concern. Based on my "search" results I'm sure its an electrical malfunction.
The problem is its hard to make an appointment for service because its so intermitting that I can't be sure it will be occurring when I bring it
into the shop. You know how hard it is to convince a service manager that you have a problem when its not happening. My factory Warranty runs
out it January. Don't know for sure if my extended warranty will cover electrical.

 

UPDATE: I did notice today condensation on the inside of the signal lens.
Nothing like that in the left side. Maybe moisture is getting in and causing
it to intermittingly short out ? ?