My USB lighting cable died today on the radio so popped the radio out and replaced the broken USB for a new one and all way good. I pushed the radio back in then then it wouldn't power at all. I checked and doubled checked and all wires were good. I removed the radio with the loom and popped it on a separate power supply and again no power.

changed the fuse etc and nothing.

by chance i touched live constant and live ignition together and the radio powered like normal ? however in the car the wires hadn't touched as they all had the correct seals in place on the bullets.

what i have to now do is like i had it on the bench both powers on the pioneer loom together to constant live to keep the radio settings, a push switch on the dash from ignition live to pioneer loom. This makes everything work how it did before the USB cable just stopped working.

What could have happened ???? its almost like the radio requires 24v to power now ????

Putting both wires together does not make 24v, its still 12v.  Most likely you bent a pin or a pin pulled out of its connector.  Did you solder your connections, how are the wires connected together?

As was said, simply applying 12V to both the red and yellow wires does not make it 24V. The yellow wire uses constant 12V to remember all your settings and the red wire uses a switched 12V to know when to power on/off.

It's hard for me to follow your post. But without the head unit installed, meter the 12V constant and 12V switched wires in your radio cavity. If either doesn't have power, the head unit will not power on and you have a blown fuse somewhere. 

Update on this.

Well I removed my radio and had it on my bench , I attached a 14.4v power supply unit to the radio and it still would not power as it would be connected to the car.

It will only power with the red and yellow power wires ran together. I have tried every configuration you can think of and that is the only way it will work. I reinstalled it in the car with constant and ACC connected and had to put a switch on ACC which now keeps my radio settings and allows the unit to power off.

The car has a standard ISO connection, no fuses blown or anything. The radio was simply removed just to swap out a faulty Apple wire and placed back in.

As was said, simply applying 12V to both the red and yellow wires does not make it 24V. The yellow wire uses constant 12V to remember all your settings and the red wire uses a switched 12V to know when to power on/off.

 

It's hard for me to follow your post. But without the head unit installed, meter the 12V constant and 12V switched wires in your radio cavity. If either doesn't have power, the head unit will not power on and you have a blown fuse somewhere.

 

The car has power as the has been tested simple by using a 12v LED on both ACC and live and both are carrying power as the LED lights.

I also removed the case of the radio to inspect the pins and non appears to be bent or pushed in. I have no cuts as I can see in the wires on the loom both car and pioneer.

I also ran power just to the pins on the radio bypassing any wiring issue.

Christ knows , wish I'd never swapped the Apple wire , just the bloody crap rubber on the things just peel away.

Update on this.

 

Well I removed my radio and had it on my bench , I attached a 14.4v power supply unit to the radio and it still would not power as it would be connected to the car.

 

It will only power with the red and yellow power wires ran together. I have tried every configuration you can think of and that is the only way it will work. I reinstalled it in the car with constant and ACC connected and had to put a switch on ACC which now keeps my radio settings and allows the unit to power off.

 

The car has a standard ISO connection, no fuses blown or anything. The radio was simply removed just to swap out a faulty Apple wire and placed back in.

Both the red and yellow wire should have 12v.

I'm questioning "AS IT WOULD BE CONNECTED TO THE CAR"???  The yellow wire should have 12v all the time and the red wire should have 12v when you turn the ignition key.  But both should have 12v to turn on. 

On the bench, just attach both wires to 12v and it should power.  One of your wires on the car harness is probably fried or a fuse is blown.  Use a multimeter to check.

Both the red and yellow wire should have 12v.

 

I'm questioning "AS IT WOULD BE CONNECTED TO THE CAR"???  The yellow wire should have 12v all the time and the red wire should have 12v when you turn the ignition key.  But both should have 12v to turn on. 

 

On the bench, just attach both wires to 12v and it should power.  One of your wires on the car harness is probably fried or a fuse is blown.  Use a multimeter to check.

No mate the radio will not work on the bench without yellow and red twisted together either with or without a loom or connected direct to the pins on the radio.

I think the radio is shot , I've had random turning off once a week for no apparent reason and had to pull over and turn car on and off to get the thing on again.

When it finally died I was following satnav and hit a pot hole and the CarPlay just cut out. I pulled up and removed the radio etc no joy, went home replaced the lightning wire with a real one and tested it , it worked and pushed it back and radio would not power.

Radio now by running red and yellow together and placing ignition live on a switch, this way the radio powers on command and I keep all the settings.

Like i said, it's your car harness which is F'd.  You probably blew a fuse or fried a wire.  Use a multimeter to check for voltage at the pins (on the car side) that would have 12v with ignition on and off. 

Like i said, on the bench, put both wires to 12v(twist them together) and it should turn on, assuming you wired the black to ground already. That's the way it should be on the bench.  The yellow wire is the main power, the red wire is just a turn on signal for the radio.  When the red wire see's 12v the radio will turn on, but the yellow wire is where the radio actually draws power.