My wife has a 2005 Mercedes ML350 (I believe it's a W163) and her A/C is blowing hot air. I'll save you the incredibly long troubleshooting background, and instead will tell you all of the pertinent information of things I've done and parts I've changed.

 

1)Replaced pressure sensor.

2)Replaced expansion valve.

3)Replaced cabin air filter.

4)Hooked up to a buddy's computer and found the compressor to be bad, so it has now been replaced as well.

5)After compressor install I hooked it up to an AC machine and ran a 30 minute vacuum.

6)Ran a leak test, and it passed.

7)Charged with 1.65 lbs of refrigerant. After this I heard the compressor come on and it briefly started to cool. After about 30 seconds it started blowing hot again. 

8)Hooked it back up to computer and found the compressor was kicked out during to high pressure. We manually removed some of the refrigerant, and then cleared the fault. Still blowing hot air.

9)I then tried to manually add refrigerant with an A/C Pro can in case there was an issue with the AC machine I was using and it inadvertently added too much. Still blowing hot air.

 

I am at a total loss as to why this is still not working. Please tell me someone has an idea and can help. Thanks in advance.

Comments

Profile picture for user MercedesMedic

Are you reading the codes from the AC unit? What are they?

Also try clearing all the codes from the AC control unit as they don't reset on their own thus preventing the operation even if there is no issue present.

Profile picture for user Markthemechanic

Okay, this has actually happened to me.

 

I would suggest you to first of all, stop driving the car. This can get really dangerous.

 

I think the fault codes are not showing the correct problem. This is not an issue with the compressor. In fact the connection between the AC system and the Engine has broke down and this needs to be fixed.

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