Was the thermal expansion valve replaced after the accident? The evaporator ices over in the time frame you describe when this valve fails to close due to defect or piece of debris stuck in it. It's a pretty rare failure mode, but it does happen. Any A/C tech should be able to verify by reading the pressures while the evap is iced over. The valve is located inside the dashboard, making the repair expensive and time consuming.

It sounds like your evaporator is icing up. I had a car that did this once - what I did was not have the hot/cold setting on the coldest setting - move it 1 notch higher. If that MB has auto climate control, don't use it, put in in manual mode but not on the coldest setting. If I'm right about what it is, putting it just off the coldest setting will allow it to cycle on/off so by doing so you won't get ice buildup and it should keep working. I see you tried turning it on/off, but if was already iced over it has to thaw, try what I'm suggesting right from the start when you start your trip.

Check the ac condenser mounted in front of the radiator(it looks like a small radiator) Make sure the fins aren't clogged up with leaves and debris.If they are,use a car wash vacuum cleaner or use the car wash to clean the debris out of those fins.If they are clean,start the car,turn the ac on,and see if both underhood cooling fans come on.If the fans aren't coming on thats a problem.The fans have to work because they remove heat from the freon when its inside the condenser.If the heat isn't removed from the freon while its in the condenser,only warm airflow will come out of the vents.One last problem to check::if the ac is on max,the fan has to be set to its highest or next to highest level or else the evaporater core( inside large housing under your dash)will ice over and little to no airflow will come out of vents and it will be warm air.The blower motor resistor may be defective causing the fan speed to only work on low speed which will cause evap core freezeup.

Air con is very difficult to diagnose behind a white screen. The only thing that comes to mind, is that the receiver/dryer is malfunctioning.

I am on a road trip right now in a 2008 Mercedes ML and the air conditioner is being very finicky. After getting in an accident and replacing the whole AC system in the car, the AC seemed to be working fine. (the temp out side is 90 degrees with full sunlight)

1. Just this morning we got in the car and it started out normally and the speed of the fan quickly dwindled. The air coming out was not very cold and the velocity of air was very small even though it was on highest setting.

2. We can hear the fan working very hard though like normal, but the air was not coming out barely at all.

3. We got out looked under the hood and saw a tube covered in ice. We also checked the air filter and it was very knew and not blocked up.

4. We waited about an hour for the tube to defrost and came back to the car to continue our trip.

5. it worked perfectly again. Just 30 minutes later, the system went straight back to not blowing any air out and being not very cold.

(We tried turning it out circulate air, and outside air and turning the whole system off for a few minutes)

With 6 hours left from our car auto shop, is there anything I can do?