Cheap Aux input EBay Purchase for Gen 1

I'd been eying that product as well. Do you have to play a "blank" CD to get it to work?

 

I bought a similar one for the 2002 Town & Country. There was a red wire sticking out of the white connecter.
Bad instructions, but it did kinda say you had to plug that into 12V.
I tapped into a power source that was only on when in the ACC or RUN mode.
It worked fine for a while. But since I bought the Prius I rarely drive it. It sits in the hot sun and I think it
effected it. One day it didn't work, until it sat in the shade for a while. Then It worked! I guess it gets pretty hot inside the van!
I might be someone else, who knows. Maybe I didn't crimp the connections tight enough, but I doubt that.
But for $25, it was $75 less than a name brand one. So it was worth a try.
And I kept my tape adapter! I was tired of replacing the belt for the cassette because you completely disassemble the WHOLE
radio assembly just to get to the belt! The 3rd time I found a belt about an inch longer and it has lasted over 2 years.
I don't play cassettes in it and the adapter just spins each spool so the radio thinks there is a tape inside. So no strain.
I would carefully re-read the instructions and check the wiring diagram and see if it says something about and external 12V supply.

 

Well, your "Important Note" says it all.
At least 1 and 2.
Does it have a separate Yellow and/or Red cable?
I would "guess" yellow is for usb and red powers it. That's what mine was.
I tried it without hooking it up.
It said to connect it to a wire that was powered all the time. But I didn't want it on all the time.
So I attached it to one that was only powered when the van was on.
You could use a test light to check the power connections on the original connector and find the ACC(hot only when car is powered).

Does the radio function with the adaptor connected? If not, then you'll need to attach a wire from the ACC wire on the original
harness and attach it to the power wire of the adaptor so you are powering the radio and adaptor.
Maybe that is why they say you need a "Y" connector.
"
2. If the radio with existing CD changer, there is need Y-adapter
Cable"

 

A cheap FM adapter has been working well for me

 

I tried those years ago. Volume was WAY too low. I had to turn the radio to full volume.
They when I disconnected, BAM! It only had to happen once before I learned!
The cassette adapter worked best for me. It was a pain replacing the cassette belt, but since I put the 1 inch larger belt
in it there was no problem.
This adaptor needs a separate power source. Thus the "Y" adaptor, OR, a red wire coming out of the harness.

 

I would contact the manufacturer and see what the deal is. Maybe you have a bad unit?
All the device does is send power to the radio telling it to play the audio from the external CD Player.
So the radio switches to that. It doesn't know if it is a cd player or not.
Apparently the radio is not getting the signal.
The adapter is malfunctioning, or not the correct one for you car.
Since it is partially working, I would suggest contacting the manufacture or whoever you purchased it
from and ask them to double check the model numbers to see if you have the correct adapter.
The wiring could be slightly different.
Or your radio is broken and even if you attack the correct deck for your radio it won't work.
All you can do is have then send you another one and double check to make sure it's the correct one.
Or the plug on your radio, or the radio itself is defective.
Maybe you can find someone willing to let you try it on there car. If it still doesn't function, you know the
adapter is either defective or not the correct one.
If it works, then you know it's your radio.
Since it does "kinda" work, I would think maybe it is not the correct one for your radio.
On my Chrysler, even though the radios looked the same, they could have a different name on the cd portion.
I believe mine is RAZ. I can't remember what the other one was RAD I think??? But I seem to recall I needed a
different adapter depending on which radio I had.

 

You failed to mention that part!
So you just bought something without checking to see if it was for your radio?
That's like buying a pair of shoes because the are on sale and finding out later they are 3 sizes to small!

 

If you are electrically inclined and have the knowledge, they you can get it to work. If not,
just order the one for your radio. It's $20!

 

I believe you are in England? I used this for my search on ebay: (3.5mm AUX MP3 Music Audio Interface CD Changer Adapter for)
Then put in your car model and year after the "for".
I am not sure if this link will work or not but this is for my Chrysler: 3.5mm AUX MP3 Music Audio Interface CD Changer Adapter for Chrysler Dodge Jeep | eBay

 

Perhaps they don't make one for your car. I've seen a few youtube videos where the person opened up the radio
and solderd wired onto the circuit board for the cd player and jumped something with a switch so the radio would think
there was a cd in the player and they played the iPhone through it.
In the long run it might easier to spend $100 and get a newer radio that comes with a USB port and Bluetooth.