AC issue-please comment
 

Can anyone clue me in? The AC in my 97 E420 under normal driving conditions works great however if the car is stopped and its hot outside the AC doesn't work..it simply blows hot humid air out of the vents. When I resume moving it cools again. Can anyone tell me what's going on?

Thanks!

check to make sure the electric fan workes. While driving you have forced cooling with natural airflow as speed increases. At idel you need the fan to run otherwsie AC will not work as gas temprature gets very high and termal or pressure cut off switch will disconect the compressor

Thanks Alpha..what's the easiest way to check for the fan..just let the car idle and look?

It depends on ambient temperature, on a 80 degree day with AC running on max. cooling and hot engine the fan should cycle on and off. If the temperature gets very high the fan(s) will stay on constantly. If the fan does not come on it could be due to faulty switch, bad relay, and burnt fuse of bad fan. You have to go through a systematic trouble shooting and if you are not versed then its better to take the car to a good technician:)

Had that problem with the same symptoms last year on the 1997 C230 (same ACC system, but differnt engine cooling system). Expert identified the problem to be a bad relay controlling the auxilary (engine) cooling fan. The relay is in the engine bay near the cooling fan stuff and is not expensive. Replacing it cured the problem. Good luck.

Thanks for everybody's help! Will take it this forum to my mechanic.

Have a great night!