You may have the dreaded evaporator problem. In which case the replacement of that part will give you access to the expansion valve. It requires removal of most of the dash and is labor intensiveas well as $$$ if you are having it done. See how the conversion goes and hope that it isn't the evaporator that's leaking..

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.