If he used the dye and you have run out, you should see the leak in the engine compartment, next to ac components. Or at the expansion valve.

If it is not present in those ares, the next logical and most difficult to look for is the evaporator. This one will also cost big $$ to fix as it is very time consumiong, althought I read somewhere on this board they generally are NOT the case.

Good luck.

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