Wire color help!

[S40Luckey]

I did the unthinkable....Whilst on vacation, I volunteered to help out a buddy with an ailing S40 with electrical gremlins. My payback for my grievous error of judgement is that I now have 2 wires that can plug into his 2002 Volvo S40 2.0t (US spec) oil pressure sensor. The harness was de-loomed because he was going to do a "wire tuck" (whatever the hell that is). I have 2(two) wires that can plug into the oil pressure sensor....a yellow and a purple. They also both fit nicely into the A/C compressor.......

My bet is on the purple wire because the oil pressure light comes on with the other, but the car runs either way. His A/C is not charged, so there's no way to test if the A/C wire is yellow or purple. Anyone NOT 6 pints into their day have an answer?

Mark