89 Mustang w prem sound yellow power wire not constant

[HemiRick]

It should be according to the diagrams I've found....I cant find a wiring digram of where this power comes from....my yellow wire is not constant.

 

[Noobz347]

Yellow is generally [Ignition On] power.

 

[HemiRick]

yellow is switched, light green is constant.....

 

[General karthief]

Yellow/ black stripe is switched power, hot in accessory and run. Comes from fuse box, 15 amp.
The only yellow wire (no stripe) is LH rear amp imput return. Is this the premium sound system?

 

[Mustang5L5]

The wiring diagram is strange.

here’s the non-premium radio. Fuse 11 is hot at all times. I think this is an error as fuse 8 powers things that do get constant power.

Here’s the premium radio. Fuse 11 is switched. Fuse 8 is now hot all the time. I think this is right based on looking at the power distribution diagram. In tjing case, the light gray is your constant

 

[Mustang5L5]

Here’s the full 1989 premium wiring diagram