PLEASE HELP! Pioneer 5100nex head unit

So basically I have a pioneer 5100nex model head unit in my 2001 Audi A6 and I’m trying to figure out if the head unit is messed up or if it’s something else. The instructions for installing the head unit say that it can NOT be installed in a vehicle without an ACC switch on the ignition and my car unfortunately does not have one but surely there’s a way to bypass that? I mean the head unit will come on and work perfectly fine if I turn the key to the “ON” position wait a second and then turn it back to the “OFF” position and then back to the “ON” position and if it so happens to not come on I gotta wait like 15 minutes and try it again and if I get the Timing just right it powers on. I have tried everything and I paid a pretty penny for the head unit bc the guy I bought the car from said he was going to take it out and I asked him “well how much do I gotta pay you to leave it in there?”. He said “extra $300 and it can stay in there” so I gave him and extra $300. I tried to explain to him the issue I’m having and he tried to make up some bs about how it does that every now and then and to take it somewhere but I shouldn’t have to do that after giving him the money for it but I should have known better. It has been doing this ever since I bought the car. I tried unwiring it and wiring It back up and that didn’t help(I know how to hook up a system btw,I’ve hooked up a system in every car I’ve owned). I ended up getting tired of messing with it so I took it out and put in this cheap ass dual head unit my buddy gave me but I’m tired of not being able to hook my amp up to this head unit so I would like to try to figure the problem out that I’m having with the pioneer one. If anyone has any answers PLEASE HELP!!

Ideally you would buy a canbus interface if it needs on, but it seems a bit early for that if I’m honest, Or maybe the headunit is knackered...

an easy way to test is to wire the red cable on the headunit loom to the yellow permenant cable, this will then make it work without ignition and confirma if it’s the headunit or the car

If that works I would then find an accessory in the fuse box and wire the red direct to that which will then turn the headunit on... I am not sure why the car has a funny ignition supply at the headunit... it maybe that it’s got a can or van bus supply to the unit and along with the data line(s) it uses that to switch the stereo on when the key is inserted, if that’s the case you may need an adaptor to make a good switch on ignition feed

if the second unit you fitted works fine then it also says to me the pioneer is broken

im presuming electronics and multimeters aren’t your strong point as that would be the first port of call if you were well versed in using them?

No I’m not very mechanically inclined when it comes to electronics but I know how to hook stuff up. Thank you for the information you gave me. I did what you said and figured it all out. I ended up having to hook up a toggle switch. Idk if it’s tricking the system to think there is an ACC switch since there’s another source of power. Everything is working good now. Super happy. You’re the man!