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#1
03-06-2006, 06:48 PM
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A/C question on W124
Took my 87 300D in today to have A/C charged. The car sat up last summer and the A/C wasn't used at all. Summer before required top off 1 lb of R12. A/C--climate control works good but obviously has a slpw leak therefore the top off---to my surprise the general automotive shop called and said the A/C would not accept a charge--they think expansion valve is blocking out the charge------is this correct? I didn't think the expansion valve did that--could anything else be preventing the charge?
TIA Joel 
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#2
03-06-2006, 07:47 PM
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yes
the expation valve is the metering device that meters the amount refrigerant that is going into the evaporator in your a/c system,and if you have any moisture at all it will freeze at that point and restict the flow .
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#3
03-07-2006, 09:25 AM
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It is much more typical for an TXV to fail open, but I am sure that it is possible for it to fail closed somehow. As the previous poster indicated, excessive moisture in the system can indeed cause the same or similar symptoms.
The good news is that on the 124 the expansion valve can be changed from under the hood. It is a job that is done in cramped quarters and requires lots of care, but can be done. If it were in my shop, I think I would recommend just replacing the TXV and when doing so, recover, dry and recycle the refrigerant. Good luck,
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#4
03-07-2006, 12:18 PM
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Larry
How did the moisture enter the system. It has never been open and only needed charging 1 time before? Seems like it would require a pretty large amount of moisture to cause a valve failure. Could there be another cause to the system not taking a charge? Thanks Joel
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#5
03-07-2006, 03:24 PM
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Yes, there are many reasons for the system not taking a charge. The only way we can help you diagnose such problems are by giving us:
High side pressure Low side pressure Ambient temperature vent temperature Refrigerant Behavior of pressures while trying to charge. This is outlined in the troubleshooting guidelines at the top of this forum. BTW the moisture does not cause the valve failure. If there is moisture, it freezes at the restriction point causing the same effect as a plugged up TXV. Good luck,
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