Low Constant Power Voltage

I'm installing a new head unit into my Jeep and both head units that Crutchfield sent to me wouldn't power on. The controls would blink but the head unit wouldn't come on. With troubleshooting with the manufacturer we discovered that the Red wire had 11.7v , yellow had 9.7v in accessory mode. With the engine running the red had 14v Yellow had 9.7. In order to get the head unit to work I had to wire the red and yellow together from the radio to the red in the truck harness. Then the unit would power up and operate. However now it loses memory everytime I turn the key off.

What could cause the constant power to have low voltage? How can I start troubleshooting this?

what year? Where did you get the yellow wire? Some years there are at least two yellow wire circuits one is for the lighting. Try turning your headlight switch all the way to the right (full bright) and see if the voltage changes.

X2. Your adapter is likely miswired. I believe the constant power wire in the 2001 vehicle harness is pink, and the switched power is red with a white stripe.