’67 Mustang constant power not working

The switched power is working, but the constant power that keeps presets in memory is not. Any ideas? Fuse in block and head unit good... Thanks a lot

just run a fused wire to the fuse box

When i had my 66 mustang, i ran a 2 guage wire with an inline fuse and combined the constant and the Acc power into one. That way you can turn on your radio without needing the key and you dont have to mess with the wiring. But if you want to keep it that way, check the fuse at the fuse box. But you will get more and cleaner power going straight from the battery. And if you run a high power amp, i suggest you wire it straight to the altenator. I had issues with mine when i had it run to the battery

I just installed in a 66 Mustang 2 days ago.

The constant 12V wire you are trying to use is obviously not "constant". I removed the instrument cluster, and ran my wiring directly off the ignition switch wiring. The ignition switch has wiring for constant 12V, ignition (switched), accessory and starter.

NOTE: I tested the ignition and accessory wires to be common to one another.

Use a multi-meter and find what fuse has constant 12v with the key off. The brake fuse should be constant.

Keep in mind that back in the 60s there were no such thing as digital clocks and presets, so most of the older cars don't have a constant 12v feed going to them.

Its also a good idea to make sure that the battery is grounded to the chassis in the older cars (learned that one the hard way).

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Kevin Pierson

hey, we installed a deck and fours a couple days ago too.  we put the deck in the glove box, and theres a constant 12volt in the wires leading up to the steering harness. I think it was just three wires.  There's an accessory here too.   It shouldn't be too hard to find as theres hardly any wires in this car.  The illumination is at the headlight switch.  ground to chassis.  shouldn't be too hard as this whole car is made of metal. 

one more tip....  it should be the biggest gauge wire you see. 

Wow, thanks for all the info folks!!! Lots of help. One more question, what size fuse should I run if I go to the ignition switch? Thanks again, you all rock!

if just powering headunit-i would do a 15 or 20

A CD player alone wont draw much current.

Stock wiring in most cars is usually 18awg. You can use that or go with 16awg it you want. Just be sure to fuse it properly.



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Thanks guys.