How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Lou P. master tech Your Own Question
Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4276
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
27644750
Type Your Mercedes Question Here...
Lou P. master tech is online now
A new question is answered every 9 seconds

I am having issues with a 2003 mercedes ML350 air

Customer Question

I am having issues with a 2003 mercedes ML350 air conditioning. It was having intermittent issues before, then it stopped working all together. I had the compressor replaced and the mechanic said that he could not charge the system enough. I tried to reset the ACC switch on the dash but it would continue cycling the flashes back and forth, but would never reset. I am beginning to think that it is electronic, like a duty cycle switch or temp sensor.
Submitted: 10 months ago.
Category: Mercedes
Expert:  Lou P. master tech replied 10 months ago.

Hello, the first thing i need to know is, does the ac off button stay lit ?

Customer: replied 10 months ago.
No it does not
Expert:  Lou P. master tech replied 10 months ago.

ok, where did you get the new compressor from? and can you give me a picture of the face of the old one and the new one? there were 2 versions, we need to make sure the correct one was installed.

Customer: replied 10 months ago.
I do not have the old compressor. The mechanic has it
Expert:  Lou P. master tech replied 10 months ago.

ok checking pics now

Expert:  Lou P. master tech replied 10 months ago.

ok perfect thanks! that is the correct one, now when the engine is running you need to make sure that the center stud on the face of the compressor is actually turning as well. can you verify that?

Customer: replied 10 months ago.
it is
Expert:  Lou P. master tech replied 10 months ago.

so so the compressor is ok so far, that is a variable swash plate compressor. it is demand based so the center spinning tells me the compressor is not locked up. so the next step is when the ac is set to cold and the light is NOT illuminated on the control panel then feel to see if the lines are getting cold at all.

Customer: replied 10 months ago.
They are not
Expert:  Lou P. master tech replied 10 months ago.

ok, did you use a machine to vacuum down the system ?

Expert:  Lou P. master tech replied 10 months ago.

also where was the compressor purchased from and does your mechanic have a code reader to read the fault codes in the ac system?

Customer: replied 10 months ago.
I can only assume he did. But i only remember seeing manifold hoses but no stand alone machine that pulls and pushes
Customer: replied 10 months ago.
The compressor was bought from parts train. The mechanic did not pull the AC codes
Expert:  Lou P. master tech replied 10 months ago.

ok so anytime the system stops function and a fault code is set the AC OFF light will illuminate and not go off, meaning that the system is locked down. so the fact that you do not have the light stuck on and it is not blowing cold tells me that the compressor is either failed or the mechanic did not function it correctly or charge it correctly. in the shop we always need to check and erase codes before the compressor woll actiuate at 100% duty cycle, the only other test you can do without a scan tool is to unplug the compressor and check the voltage when the system is sett to full cold. if you have voltage then the compressor is either failed or the charge is way too low.

Customer: replied 10 months ago.
What voltage does it have under duty cycle
Expert:  Lou P. master tech replied 10 months ago.

battery voltage, so say you set the ac to slightly cool it may have 5 volts, but when set to max cool it will have the same voltage as the battery (about 12-14.5) to activate 100% duty cycle.

Expert:  Lou P. master tech replied 10 months ago.

did you find anything?

Expert:  Lou P. master tech replied 10 months ago.

are you still needing assistance?