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2005 ML 500
Black, 18" AMG Wheels, 285/60R18 Falken Ziex ST/Z + Bi-Xenons(+ Drew's e-code mod), Yakima roof bars. Former vehicle 2001 ML 320 with 108K miles, when traded, and a large repair/defect history.
When the truck starts blowing ambient air you must leave the truck running, open the hood and check to see that the clutch on the front of the compressor pulley is turning. If it is turning, then you have an Air Mixture Door motor problem. If it isn't turning then you have an elec. problem or a low charge problem.
When the truck starts blowing ambient air you must leave the truck running, open the hood and check to see that the clutch on the front of the compressor pulley is turning. If it is turning, then you have an Air Mixture Door motor problem. If it isn't turning then you have an elec. problem or a low charge problem.
Interesting. I thought I did feel the A/C compressor cycle on and off during the time when it was blowing ambient air. Not 100% sure though, I will check the compressor pulley tomorrow...if the problem happens again tomorrow.
Vehicle: 2002 ML 500, 1994 Ford Explorer donated to Doctors without Borders
Location: Boston, MA
Posts: 2,029
Did you check to see if your system is charged? I'm going through the same thing now. It took me 15 minutes to charge it yesterday and I have cold air. I'm watching to see if it will remain charged. If you have no refrigerant, nothing is going to work.
Sorry, yes, the CLUTCH on the front of the pulley is not turning during those times when the A/C blows hot air. It is turning when the A/C's blowing cold air.
PS: Thank you for the effort of scanning and uploading a pdf, that's above and beyond the call of duty!
Being that your A/C worked for one month, it is safe to assume that a non signal from the AAM would have surfaced during that time. So the only logical conclusion is that during the month after the mech. charged your system, the truck has lost enough refrigerant, causing the system to operate on a "sometimes" basis.
Yes it is true that the AAM (in this model year) turns the compressor on, but I still believe that something is telling the AAM not to turn on the compressor and that the AAM is not the problem. Remember that replacing the AAM is more involved than what your mech. believes. It will have to be programmed by the dealer only, since among other things, it includes your key recognition system.
Look at the pdf below and inspect all the A/C lines, and see if there are traces of refrig. oil anywhere; that would indicate a leak. Also remove the elec. 3 wire connector to B12(Pressure Switch) and see if there is any trace of corrosion, (usually green).
My suggestion would be that you go to another mech. who has an evacuation/recharging machine, and simply ask him to recharge your system and attempt to find the source of the leak and see what his opinion is. Absent any under-hood leak, and based on the age of your truck, I'm afraid that you have a leak in the evaporator which is behind the instrument panel, which is super expensive to replace.
Do not tell the mech. that you were elsewhere or that this forum suggested anything, simply ask for a recharge and check for leaks. If he can't find any leaks and it is properly charged, I can almost guarantee you that the system will work trouble free for another month or so, until the refrig. has leaked out again.
43sqd,
On the PDF file you posted, which one is the evaporator, part #2 (maybe?). I believe the expansion valve should be there also but I don't think is marked. I know this has been an issue in a recent thread in which some of you most knowledgable ones were contemplating a clogged expansion valve. Acorad said at one point that his mechanic purged some of the cooling agent the due to overcharging. Could that high pressure detected be because of a clogged expansion valve? in which case purging some of the pressure in the system would make the problem worse.
Linear Mode
