PortAxePlayer1

Hi There!

After thousands of hours poured into the W210's restauration, I still have one thing that seems to be eluding everyone at the dealership and myself, but hopefully not this community!

A bit of a background on the initial issue:
LO/LO -> Cold Air on both sides
HI/HI -> Hot Air On Both Sides
22/22 -> Oven on the left, correct temperature on the right (or the inverse on rare occasions)

Main culprits are usually low charge or a bad Duo Valve -> System was fully charged and a new Duo Valve was installed, nothing modified the behavior above.

An issue that was present was an A/C that only cooled on acceleration, with very poor cooling on idle or cruising -> Bad A/C Compressor, replaced it with a new one + new dryer and lines and the cooling was now excellent, but the initial issue was still unresolved.

Fast forward to winter, putting the A/C on HI/HI in defrost mode started spewing white specks out of the vents -> New Evaporator, New Heat Exchanger, New Expansion Valve & every O-Ring/Piping related to this. A Flap test revealed a bad Vacuum Control unit (the one behind the A/C Filters), this was replaced and the flap test was done successfully.

After all of that, the A/C still shoots hot air worth baking bread on the left side, sometimes on the right. I saw some posts suggesting it might be the temp sensors, yet the testing as follows shows nothing wrong (temps in C)
#1 - 22
#2 - 24
#3 - 82 (baking)
#4 - 22
#5 - 06

Evap Sensor shows a perfectly correct temperature as well.

The A/C Diagnostic showed only one error which was B1421, the Pulse Module but couldn't find much info about it here.

I'm heading towards incorrectly connected Vacuum lines, not really sure what else there is, what do you guys think?

Plutoe

you dont have all the data, clear the fault and run the test again and post all the data points from 1-8

PortAxePlayer1

#1 24
#2 16
#3 71
#4 16
#5 08
#6 84
#7 07
#8 26

With both sides set to 22C

Plutoe

number 7 should be 15 to 17 therefore you either are low on on refrig or a faulty compressor that cant make pressure-----you also may have issues with your duovalve see the temp difference between 3 and 4

PortAxePlayer1

Thanks for the reply Plutoe!

However, we can rule out all three components as they are all brand new from Mercedes and were all replaced earlier this year by the dealership.

As mentioned in my initial post:

• New Compressor
• New Duo Valve
• New Evaporator
• New Heat Exchanger
• New Expansion Valve
• New Dryer
• New AC Vacuum control unit
• New Filters including Charcoal
• Full System Recharge, no leaks deducted, no hissing

I have no issues in cooling or heating, when Lo/Lo the air is ice cold, when it's Hi/Hi it's very hot.

It's just when I set temperature to anything different than Lo on the left side, it always shoots heat on this side, nothing else. The right side is properly mixed though.

Only error code is as mentioned in the first post, when I did the reset I noticed that the right side started having this behavior instead of the left side, then after a power cycle the issue is transferred again to the left side.

Extremely odd, maybe a bad AC Control Unit?

Plutoe

if what you post is the truth then you cant read data correctly or you got snookered my someone because the data indicates low on refrig and or bad compressor plus a faulty duo valve