Exterior mirror heaters ON 100% of the time. Yours too?

Thanks to a member at SCOA I learned recently, as have many others, that the exterior mirror heat seems to be ON 100% of the time, even on very hot days. They don't just come on for a minute and go off. They're on all the time while the key is ON or the engine is running.

The manual says, "The exterior rear view mirror heating is switched on automatically at low ambient temperatures." This is logical and seems like a nice feature for those cold times in the parking lot. However, contrary to the wording, the heaters come on and stay on regardless of temperature.

I'd be really surprised if this is what was intended. I can imagine a number of issues with this setup.

There's now a Poll about this topic. Click on "polls" above, and let us know if yours are doing the same.

Views: 54

Reply to This

Replies to This Discussion

GLSONN, it's easy to tell if they're coming on. Touch the mirror before you start the car, then touch it a minute later. Then at the end of a drive, and you'll likely find they're still HOT. Much hotter than ambient. Alternatively, just turn the key to the ON position (I position) and within a minute they'll be heating up.

If it's in the 90s all day long in Houston do you really want those heaters cranking away the whole time? It's likely to shorten their lifespan and puts an unnecessary load on the alternator, or drain on the battery if the engine isn't running.
It is my understanding that they are set up to be always on on the 451... that said, there have been numerous complaints about this feature pretty much everywhere the 451 is sold.
It is supposed to be converted to turn on with the rear defroster, like many other cars, as a running change on the 2009's.
UNBELIEVABLE!!! Just checked car in garage. Garage temp 79 degrees. Turned car key on and sure enough in less than a minute the outside mirror got warm. This has to rank as the absolute dumbest engineering feat Mercedes has ever accomplished. Might have been able to squeak out an extra 1/2 to 1 MPG without this load continuously on the alternator. And to think how easy it would have been to make it right. Blows my mind. Penske, Daimler--are any of you listening??
As may of you are in warmer climates, pretty much all year round.(I'm in Calif) Seems like we should just be able to unplug the mirrors.
Whenever my Ford PU mirrors are foggy in the morning, I just run a squeegy over them.
I got an email from Walter Grassi, the business manager at the Smart Center Indianapolis.

smart NEWS

TO: 'smart drivers'

FROM: smart Center Indianapolis
SERVICE & PARTS : Joe Taylor

The 2008 Heated Mirror Function has been added

Outside mirror electrical and adjustable/heated (V21)
The exterior rear view mirrors will be heated automatically.

Switching on: Make sure the key is in starter switch position 1. The exterior rear view mirror heating is switched on.

Switching off: Turn the key to starter position 0. The exterior rearview mirror heating is switched off.

Joe Taylor
317-580-6801 Ext: 252

Walter Francesco Grassi
Manager, Business Development
World Wide Motors
317-580-6800 Ext: 212

Visit our Website
It appears smart is trying to put "lipstick on a pig" so to speak, by making it sound like what we all perceive as a negative is actually an improvement, hence their comment that the "2008 Heated Mirror Function has been added." Thank you very much.

On the SCOA forum the general consensus now is that the 2008 manual was incorrectly worded, and the new wording should be as stated in the above letter from smart. It appears the 2009 model may be rewired to have the mirror heat come on with the rear defroster heat. A welcome improvement.
Don't have my smart yet, but if one is able to remove the mirror and unplug the heater wire, any ideas on how difficult it would be to just add a switch. I absolutely don't know, but if it's easy to unplug, that would seem a viable diy mod. Thoughts?
I like Roger's idea. & Just add a small toggle switch under the dash. Or better yet, if it doesn't overload the fuse, how about rewiring the mirrors to the rear defogger like it should have been done in the first place.
I thought I read on the SCOA site from a factory worker that the 2008 version the heat was on all the time and in the 2009 they were going to tie it into the rear defrost?
I will let everyone know in about 2 months when my smart arrives....
I check mime and is warm too , but im going to live it like it is , this circuits puts a load on the electrical sistem but a drain resistor is good for the sistem it will protect the circuit from a spike or surge in voltage from the alternator .And only works withe the key on the ignition.And the draw is minimal...
Here's a link to a very nicely done and well illustrated DIY mirror heater switch:
The DIY Mirror Heater Switch is a great idea and very nicely documented. But has anyone wired the mirrors up to the Rear Window Defroster?

Reply to Discussion


find a

smart center



  • Add Photos
  • View All


  • Add Videos
  • View All

© 2017   Mercedes-Benz USA, LLC.   Powered by

Badges  |  Report an Issue  |  Terms of Service