A/C Compressor Not Engaging?? Troubleshooting
Thread Starter
Junior Member
Joined: May 2010
Posts: 25
Likes: 0
1999 Mercedes ML430
A/C Compressor Not Engaging?? Troubleshooting
My '99 ML430 a/c compressor is not engaging and I cannot figure out why yet. I have enough refrigerant in the system and the compressor is not seized (can spin the clutch freely by hand), but I'm getting nothing from it when the system is running.
Can anyone help me with troubleshooting this compressor problem? I was thinking maybe a faulty pressure switch or unplugged power line, but I'd just like to try and determine the problem without removing it from the engine, if possible. I also apparently have a oil leak that has sprayed all over the place and made it pretty messy down in this area.
Any help with this diagnoses is greatly appreciated!! Thanks in advance!
Can anyone help me with troubleshooting this compressor problem? I was thinking maybe a faulty pressure switch or unplugged power line, but I'd just like to try and determine the problem without removing it from the engine, if possible. I also apparently have a oil leak that has sprayed all over the place and made it pretty messy down in this area.
Any help with this diagnoses is greatly appreciated!! Thanks in advance!
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Please answer the following questions:
1. when you press the AC button, does it illuminate?
2. how do you know that there is sufficient refrigerant in the system? Be specific, no assumptions or guesses.
1. when you press the AC button, does it illuminate?
2. how do you know that there is sufficient refrigerant in the system? Be specific, no assumptions or guesses.
Thread Starter
Junior Member
Joined: May 2010
Posts: 25
Likes: 0
1999 Mercedes ML430
I connected a PSI guague to the low port and pulled 36psi, which I thought was correct?
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Please read about Static Pressure.
90% of AC systems not working after change of season layovers are attributed to loss of refrigerant (small leak).
You are probably low on refrigerant, as the system will not operate if the pressure is too low or too high and you should have it repaired professionally.
90% of AC systems not working after change of season layovers are attributed to loss of refrigerant (small leak).
You are probably low on refrigerant, as the system will not operate if the pressure is too low or too high and you should have it repaired professionally.
Member
Joined: Oct 2012
Posts: 244
Likes: 1
From: Columbus, OH
2002 E55 AMG, 06 C55 AMG, 72 350SL
As for the oil leak, I would clean up the mess with brake parts cleaner. Then drive the car a little bit and see where it is coming out from. It is going to be harder to diagnose where oil is leaking from, when there is already oil all over the place.
Thread Starter
Junior Member
Joined: May 2010
Posts: 25
Likes: 0
1999 Mercedes ML430
LEAK FOUND
I found the leak in the A/C last week. Looks like it is coming from the expansion valve. Going to let the new refrigerant I have drain out then replacing it when it does.
As for the oil leak, a guy from Aamco said what we figured (oil cooler seals), so I replaced the seals. I've only driven the car a little bit since and plan to more this week, but it seems that it is still leaking somewhere. To note: the oil expansion cover at the timing case has been replaced and now the oil cooler seals replaced.
If anyone has any suggestions on this, I'd greatly appreciate it. This has been very hard to find!
As for the oil leak, a guy from Aamco said what we figured (oil cooler seals), so I replaced the seals. I've only driven the car a little bit since and plan to more this week, but it seems that it is still leaking somewhere. To note: the oil expansion cover at the timing case has been replaced and now the oil cooler seals replaced.
If anyone has any suggestions on this, I'd greatly appreciate it. This has been very hard to find!
