tobe1424

I have about 110K miles on her and for some reason, the driver's side blows cold while the driver's side blows warm. This can be a nuance in the SFL heat. Anyhow, I connected my Autel scanner and I get no hvac codes. I've searched a few forum threads but none confirmed what fixed the issue.

Is there any common or easy fix for this? Where can I start? I hope to not have to remove the entire dash for this one.

Many thanks in advance.

juanmor40

Can you see the HVAC live data using your Autel scanner? Is this Autel scanner MB specific? Does it have actuation functions such you can actuate the HVAC motors?

You want to verify your AC system pressure and temperature at the different sensors that control the HVAC

S. Madman

Search is your friend. https://mbworld.org/forums/e-class-w...nger-side.html

juanmor40

If @S. Madman suggestion works for you, I would not consider fixed but maintained. Then, add it to the list of things to do periodically. Perhaps something like oil changes every 5K miles + HVAC vents actuation hot<->cold. Like birthdays + license plate renewals

CaliBenzDriver

DIGITAL HVAC FLAP ACTUATOR


Quick solder epair opportunity
A pulse counting chip decides when retirement date comes : "*useful life expired" flag.


soldered module + lubricated gears

The technology is so advanced it requires tuning all the time.... LOL

Working on these is like free diving for wild abalone shells... ouch!
There are half-dozen of these actuators in charge of managing air vents. No one is sure what position does what exactly... they are ALL identical units built to quit rapidly given higher currents from dry gears.

Use a SCANNER on HVAC Module to read data... these actuators are networked over two pins that suggest CAN rather than LIN.
​​​
All state of the art goodies * just kidding✌️

tobe1424

Thanks, I will give that a try.

Calibenz, thanks a bunch for the details. I will hook up my scanner and take a look at the HVAC module. However, I am not too sure what to look for. Where is the DIGITAL HVAC FLAP ACTUATOR located? Is it a pain to remove?

Cheers

CaliBenzDriver

yeah, agreed:
a whole can of pain is involved with these actuators. It may be the HVAC internal pins that are loose - HVAC firmware packs a lot of tricks with bumper sensor, line pressure... supersonic sound effects...

konigstiger

Consider checking refrigerant.

MBENZTECH

Yep....... Like Konigstiger said............ Check refrigerant level. It's a common thing with Mercedes vehicle when they have low freon.

juanmor40

To the OP: what are you after? AC cooling again, or finding the root cause of why the AC is not cooling and getting it fixed so it cools nearly as new?

If @konigstiger and @MBENZTECH are on the money (and they may be), you must get the "current state" well documented before evacuating the AC system; otherwise, once evacuated the "evidence" is gone. Let us assume, it lacks enough refrigerant and once evacuated/recharged cools again, then what? closed chapter? or questions like:
1 - why was there less refrigerant in the system?
2 - how much was missing?
2 - is it a leak? or average loss of the system?
3 - if it is not normal, how long before it happens again?

I think the system must be evaluated using XEntry plus a set of AC pressure gauges to understand what the cooling system side is trying to do, i.e. right pressures, correct behavior under load, evaporator temperature (XEntry), etc. If the system passes the pressure gauges and XEntry, you/the technician can isolate the problem into: an external problem (sealed cooling system outside the cabin), or an internal problem (cabin internal issue with actuators, blower, etc)

My 2014 W212 AC system is still on its original charge, circa Feb 2014, and still cooling as expected. The clutch died on me, but no need to take the compressor out (separate thread). I honestly avoid opening/evacuating the AC system as long as I can since it opens another can of worms.

CaliBenzDriver

With W212 A/C many factors can help cooling become marginal. My favorite is the lazy compressor valve championed by @juanmor40

To best match problem with solutions we just need to gather evidences.

Investigating lineset pressure with a gaugeset disturbs the pressure ports and increase the chance to have a slow leak...you go looking for leak, then you get one!


> PRO vs. DIY:
Opening the A/C sealed circuit is a very legit professional step for paying customers.
Good DIY'ers try not to create more problems than they fix.

> New Crops...:
As Juan pointed out the W212 A/C is primarily not a leaker... MB has developed a new range of sofisticated issues to gently degrade cooling.
Wholesome failures no longer require old fashioned leaks... that was bad for EPA rulings.

Everyone proceeds as pleased with their own bias of non-profit vs. for profit. When we learn to troubleshoot chaos it's a good day.