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Are there problems with air conditioner freezing up?

(2007 Mercedes-Benz S550)
in Augusta, GA on June 24, 2012
42,000 miles with no prior ac issues other than blower motor failure at 40,000 miles. On recent trip, the airflow diminished to barely detectable after 2.5 hours of a road trip with both thermostats on auto at 77 and an outside temp in the upper 80's. The fan speed would audibly increase with higher settings without increase in flow. Returned to normal after parking an hour. Functioning normally since on local trips.
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Popular Answer
on July 19, 2012
I have an 07 S550 with 33k and it did the exact same thing today with same symptoms after long road trip. Airflow returned to normal after being parked for a while.
on July 19, 2012
Discussed the issue with the service advisor at the dealership who didn't have a clue. Didn't bring it in since it functioned normally. Have had a couple of 2+ hour trips since in ambient outside temps of 98-100f without further problems. I've experienced this in early 70's cars with ac's that were not integrated with the heating system as well as in window unit home air conditioners. Please advise if this this recurs or if you find a fix. Will do the same
on August 07, 2012
My 2007 Mercedes S550 with 19,875 miles also froze up after 5 hours non-stop on a road trip. Stopping for 30 minutes allowed the ice to melt, but on my next 5 hour leg, it froze up again. MB of Georgetown, TX said the freon level was correct, but replaced the Temp Sensor in the Heater control box. That did NOT fix it. On my return 5 hour non-stop drive, it froze up again. Stopping once again for 30 minutes allowed it to work for another 3 hours before it froze up again. MB in Montgomery, AL replaced the blower motor and blower control relay, suggesting resistance was building up in that particular system, slowing down the blower motor, and thus allowing the evaporator to freeze up. Will be taking a long drive this weekend to see if that cleared it up.
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