resqguy77

I searched this forum for the last hour and couldn't find a similar issue (unless I missed one).

2012 ML350 Symptoms:

1. Most of the time the AC works great and is very cold but, occasionally, upon starting, it takes a long time for the AC to get cold. I checked the high and low side pressures with my manifold gauges and they seem to be within proper range.

2. On longer drives, the air flow from the vents slowly reduces even with the blower motor on high. The blow motor is working, but it seems like the air flow is being restricted somewhere. Changing the vent location (i.e. floor, floor and dash, defrost) seems to redirect the air, but the air flow is very weak. The defrost is almost nothing. Then, after stopping for a bit, or the next day, the air flow is back to normal.

I have a Foxwell NT710 bi-directional scanner with a Mercedes software package. There were no faults or codes in the HVAC system. Not sure what else to look at on the scanner.

Any help is greatly appreciated. Thx!

CaliBenzDriver

Read the pressure and temps with your scanner.

How old is the cabin filte, good flow?

At the end of the day compressor use a proportioning valve that often need service.

resqguy77

Here are a couple of screenshots from my scanner. I replaced all three cabin air filters about a month ago. Thanks!!

CaliBenzDriver

Very good news!!

this shows refrigerant circuit ok

Your scanner and efforts just saved you a big bundle of cash.
Refrigerant compressor is working well.


Cooling is still limited on side by either bad solderless flap actuators or vents are manually shut off or partially closed.

The AAC module would report active faults for failed actuators. Double check that and/or use your scanner to directly command actuators.