Illumination Wire On A/c Unit

[RANDY]

I have a spare A/C unit, and I want to light it up for the purpose of taking photos of different lighting methods.

Is there any way of finding out which pin on the back of the A/C unit is used for illumination?

Cheers in advance!

[RANDY]

My god I love my multimeter! Is there nothing it can't do?

I couldn't think how to test the socket initially, but during my lunchbreak it popped into my head.

All good, cheers!