I know this problem isn't isolated to the F700BT as I noticed it with another headunit I was testing. However I thought the smart minds here would be able to help identify it.

 

Properly connected (black-black, red-red, yellow-yellow) to the correct Metra harness the headunit does not turn on. A DMM shows nothing on the yellow leg of the metra. If I jumper yellow to red from the headunit so both have switched power, the headunit turns on.

 

I'm not sure why headunits would not turn on without the constant (I thought that was just for memory stuff). I'm assuming this is either a known issue or I have some blown fuse or something. What would cause the constant from the car to have nothing? I can certainly strip it and check it before the factory harness (it looks to be a green/black wire) but figured someone here with more knowledge would know the answer.

 

Thanks!