Still can't believe that this isn't a Sticky. They should make one with Retiredwarhorses consolidating all the wisdom he dropped on us within the 7 pages of posts.
Anyway, swapped a one for one between two (fully functioning) machines. One with the old PCB & GPC, the other with the newest S3 and TSU. I ran them before beginning, both had a solid yellow wait light and both started immediately in 40 degree weather. I completed the box swap, but didn't do the GPC & TSU swaps. I decided to try to start them both. The one with the new S3 box and old GPC had a blinking wait light, but started fine. The one with the old PCB box and new TSU had no wait light and didn't start. Obviously, I'll swap the TSU and GPC out tomorrow and it'll be just fine.
Question, how jacked up is it to leave the new S3 box with the old GPC if it is working fine, just with a blinking yellow light instead of solid?