pom2ter

hello MB friends

i have a little issue on my 2013 w212 350 cdi 4matic...

on hot day , when i put my AC on auto for a long trip , air flow start to slowly decrease after 20-30 minutes , and at a time there no air flow at all on air vent.. if il try to use manual setting for AC , and put blower to max speed , there is no air flow on air vent but i can hear the blower on the dashboard running hard.

after that , if i cut off the AC , en st air flow setting to front and speed 4 ( for example ) , air flow start to increase slowly , and reach normal flow after 5 - 10 minutes ... air is cold for 5 -10 minutes too ...
and when i put AC ON again , all is ok but it start to decrease after few minutes..

for me it's like something is freezing on AC system and stop air flow until i cut it off .... and de-icing

maybe someone have same issue and a solution

thx for reading ( hope you can understand my english " )




this will not be a problem in few months

ygmn

do you feel coming out anywhere? Dash, floor etc?

Have you checked Cabin filter?
IS evap all nasty and cloged with yucky stuff?

Any AC codes?

IS blower motor OK IE is bower cage still strongly attached to shaft?

pom2ter

hello

no when air flow decrease , there is nothing coming from air vent... cabin filter is 6 month old , in last service but i'll check this

also , no bad smell or something like that.

S-Prihadi

The symptoms sure sound like a freezing EVAP.
Get a decent scanner, Launch Creader Elite for Benz...cheapest but most powerful for the money for BENZ ONLY.
When car has shut down for 12 hours, read all the temperature sensors at N22/7 HVAC computer. Engine OFF, only ignition ON.
There will be EVAP temperature sensor there. See what value it is reading against all other temperature sensors.
Hopefully it shows drifted value even at ambient temperature of what you have now. 2C difference is OK.

MB setting for EVAP maximum cold is no colder than 2C to prevent freezing.

Run the HVAC and see how how low does the EVAP temperature sensor read till the moment EVAP frozen ( no air flow ).
There you can see its actual drift value.

Perhaps with that baby Launch you may picked up trouble code if any.

Good luck

kajtek1

Starting with sensor calibration test, as S advise is the easiest way to troubleshoot and that will also give you static charge of refrigerant,
Than for compressor test you need hot day as variable speed compressors need to be forced to max for proper output reading.

nc211

My bet is a freezing up EVAP coil underneath the center stack dash. If you pull the cabin filter from the passenger side footwell and get a tube camera from a tool shop, fish the camera into the duct work that is closest to the center stack, you'll likely get a view of the eval coil to take a look. You may need a cleaning if it's all gunked up with dust and crap like that. If it's clean, then you probably have a leak in the cooling line or compressor. When coolant gets low in HVAC, the coils will freeze over. Same on your home units too.

See if you can get a cheap tube camera and snake it into the duct work to see it, would be where I would start. Also pretty easy to have the ac pressure tested to see if you have a leak (you'll know if the pressure is low).

pom2ter

thx all for advice , i'll try search for all your advice ... yesterday no issue at all , but temperature is not so warm as this summer.

for sure pressure is ok in the AC system ..

nc211

Another way to check if it’s freezing over - when airflow stops or noticeably reduced, turn off the ac and turn up the heat. If airflow improves after a few minutes, you’ll know…