No Gauge Cluster Lights

[81Blackbird]

I'm posting this question for a friend of mine that is not very savvy with the internet.  He's 83 and needs some help.  After taking the dash apart to install a new A/C system he is without lights for the main gauge cluster only.  I told him about the small metal strap that connects the light switch to the gauge cluster.  That is in place.  I asked him to check the fuse and it is okay.  Being a 1970, not 70 1/2, Trans Am I felt that the P.C. board may need to be replaced. I sent him the link that Firebirdparts posted this past January.  He sent me a picture of a 3 inch brown wire pigtail that comes off the plug that connects the harness to the back of the light switch.  He doesn't remember where it goes but it is hot when the ignition is on.  Does this wire connect to something that fires up the lights to the gauge cluster?  Any help would be greatly appreciated and I will forward any suggest to him that anyone may have. Thank you in advance for the forums help.

I'm not very savvy myself because I can't get an image file small enough to post. 

[81Blackbird]

test

[Wallington]

I think there's a brown live wire plug on a 69 model to the heater switch. But there's likely other live brown wires as common for accessory options, similar to digital clock in later 2nd gens.

[81Blackbird]

Thank you Wallington.  It didn't look like that plug would do the trick.  I will find some time and head over to his place to see if I can give him a hand.  I'm thinking it maybe the PC board.  He drove to Pigeon Forge this weekend for the show, maybe next weekend.  Thank you for your input.