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So basically ur saying that the AAC Module could have gone faulty ?
I’m going back to the garage today and I’ll ask them to clear codes on the module with diagnostic tool. Hopefully that should sort the issue out.
if not, I’ll get the module from the breakers yard.
fingers crossed 🤞
Nope, I am not saying to replace more parts...
READING AAC Module codes and data streams with scanner is to troubleshoot what's happening.
Right now you have all new A/C parts and it's not working... perhaps it's time to start diagnosing your issue, like proportioning valve PWM signal ....
Last edited by CaliBenzDriver; Aug 14, 2024 at 04:36 AM.
So basically ur saying that the AAC Module could have gone faulty ?
I’m going back to the garage today and I’ll ask them to clear codes on the module with diagnostic tool. Hopefully that should sort the issue out.
if not, I’ll get the module from the breakers yard.
fingers crossed 🤞
please do not continue changing parts w/o diagnostics. It will make things worse, more difficult to pinpoint.
These cars are a collection of computers and sensors to control a few devices. There are many failure point besides the "main visible" parts such as compressor, condenser and evaporator. For example, fuses, hoses, wiring, seals, modules, etc. Be patient.
On the scanner, there should be a list of modules. One is named AAC. Within that module entry, there should be entries for error codes, and another for live data.
Please take a snapshot of the live data under different conditions such as AC set at MAXCool at idle, and at 1500 RPM
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Get a Mercedes-specific scanner or a copy of XENTRY and scan for codes. If the AC coolant pressure is too high or too low, it won't work. You may or may not get a CEL on the dash, so you need to scan.
If your new compressor is not genuine or let say an aftermarket one claimed to be suitable/compatible in most ways BUT if it uses the wrong type of control valve on it ( with or without diode version is the question), that alone will not allow AAC module to operate the compressor.
If your new compressor is not genuine or let say an aftermarket one claimed to be suitable/compatible in most ways BUT if it uses the wrong type of control valve on it ( with or without diode version is the question), that alone will not allow AAC module to operate the compressor.
My cousins car was there for a full service and gearbox service, the mechanic tried his compressor on my car and it still didn’t work.
Last resort is now to check wiring around the oil cooler and rocker cover gasket, in case the previous garage clipped the wire without realising.
What engine is yours ? M271.8 EVO petrol or diesel ?
With proper scanner and a DMM with duty cycle function it is easy to test and see if the commang signal to control valve of AC compressor arrived at compressor or not ?
Your compressor is clutchless or has the magnetic clutch ?
If there is a magnetic clutch, you need to check if the clutch get POWER or not too.
My E400 and my friend's W204 C200 with M271.8 EVO are without magnetic clutch.
Both cars in its AAC module ( need proper scanner ) will show the command amperage to the compressor control valve. Maximum is 1 AMP. Usually the command is 0.95A during initial start and
0.50 ish amps when AC already cool.
What engine is yours ? M271.8 EVO petrol or diesel ?
With proper scanner and a DMM with duty cycle function it is easy to test and see if the commang signal to control valve of AC compressor arrived at compressor or not ?
Your compressor is clutchless or has the magnetic clutch ?
If there is a magnetic clutch, you need to check if the clutch get POWER or not too.
My E400 and my friend's W204 C200 with M271.8 EVO are without magnetic clutch.
Both cars in its AAC module ( need proper scanner ) will show the command amperage to the compressor control valve. Maximum is 1 AMP. Usually the command is 0.95A during initial start and
0.50 ish amps when AC already cool.
My engine is 651.924 diesel and has a magnetic clutch.
You then have two wire set to trace for command for AC compressor.
The magnetic clutch is easy to FORCE on using wire and a suitable sized fuse to provide constant battery power, but do not do the same for the control valve please, as it may get damaged
from overheating unless PWM signal is being fed to it.
Any good hvac worshop can figure this out, but his scanner must be decent to be able to read N22/7 AAC module live data like below ( below is using Xentry )
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