El Cid

I checked with MBUSA Customer Care rep. who checked with a product specialist. On 2010 models, you can just turn climate control system off instead of activating the recirculation per Operator's Manual. This accomplishes same thing to protect the filtration system.
Problem with activating recirculation is that once car is turned off and then back on, recirculation is automatically deactivated. (More German engineering) Which is what happens when you leave the car and then an attendant comes to move it to the conveyor. Unless you leave it unattended and running.
Hopefully they know what they are talking about.

thefisch

Good info. I wonder if that applies to later models too...

El Cid

I read on another thread here about MB manual recommending the off method on later models. My manual specifically stated to activate recirculation. That's why I contacted MBUSA.

Airmousam

Cid, good job on the follow up! I just shut mine off when going thru the touch less. No issues

El Cid

I made the following instructions and leave them on steering wheel. In 20 pt. letters. My car is not keyless go.

AT START OF CONVEYOR
Engine Running;
Press and Hold brake pedal;
Shift to N;
Release the brake pedal;
Switch ignition off and leave key in.

DO NOT USE BRUSH ON CAR
Please leave this sheet in car.
Thank You!!!

Alex.currie44

This conversation was around a while ago.
In all my 7 cars over the years I never bother about shutting the HVAC system off or into recirc mode. Never had an issue either.

El Cid

Let's hope your good fortune continues. The only reason I brought this up was because it is in the Operator's Manuals for MB vehicles. I have never seen anything like it in manuals for other makes I have owned.
Perhaps it is an overly defensive disclaimer by MB just in case something happens?

porksoda

The only reason i can think why the manual says this is so outside unpleasant odours don't come in along with moisture.

Alex.currie44

One way to treat odours in your HVAC system is to put about 2 tablespoons of hydrogen peroxide in about 1-2 cups of water in a spray bottle.
Spray this down the intakes where outside air enters the system with the car in both heating and cooling modes. Hydrogen Peroxide will kill off the bugs that cause the odours.

Haffster

That's what the SA advised me as well (for all cars); shut the HVAC off in car wash.