It should be the one closest to the battery. If your ac is working at all, it should be cool, rather than hot when the ac is running. This can be a tricky thing. You really need to check the pressure to make sure your system needs the extra charge.
95 Contour Zetec, ATX (wrecked, sitting in the barn)
95 Mystique Zetec, MTX
2000 Taurus SEL 3.0L Duratec
1994 Crown Victoria LX 4.6 V8
1993 Chevy Silverado 4.3 V6
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