Tricking a car radio aux input?

Sorry if this is off-topic, I just usually get good answers here, and not sure where else to post a question like this:

I am using my car's auxiliary input (2005 Chrysler Pacifica) to play audio out of my android phone (could be ipod/iphone, etc.).

This works, except the way it works is the radio detects the audio signal and automatically switches between playing CD's in the multi-changer and the aux input. This means when there is a pause in the audio, it switches over to CD, then back when the audio comes back. Usually there is a delay. It makes phone calls basically impossible.

So, I am wondering if there might be a way to fool the aux input circuit.

There is a video in, so one thought was maybe a signal/voltage could be applied to that line, since I do not care about the video in, thus hopefully tricking the radio to keep aux in active.

Otherwise, possibly there is a way to wire up some kind of circuit to make it think there is an audio signal, even during silence?


Yeh, you will need to do some experimenting, but putting out a very low signal / very high signal in Hz should fool it and not generate noise (pick outside of the human hearing range).
What might really be happening is the device is not outputting during the period of silence (i.e. the headphones are actually going ‘off’).

Check it with an oscilloscope to be sure (or some other device that outputs audio via headphones and doesn’t suffer the issue…

Might also pay to read if the stereo can disable that feature.

remove the CD from the CD player ? (or is that too simple?)

Nope, already removed all the CD's. When it detects silence, it switches back to CD playing mode, instead of aux input. So even though there is not actually a CD, changes back to that mode and says 'no disc'.

Are you sure it is doing it by sound detection? Most devices use a micro switch in the jack.

I am pretty sure, since plugging it in does nothing. It only switches when I push play on a song for example.

Most video inputs detect if there is 75 ohm on the input line. try putting A 75 ohm resistor on the video input and if that works you can build A little box with A switch to enable your input.

Probably, you've sold your car by now and no longer need this information. But hopefully other can use the info. During my search for the same problem, I came up with solution or, at least, understanding.

The DVD player which AUX inputs are connected has devices in the circuits to detect sound level as you've guessed. I wish I can upload my picture but i am new to this site.

Once DVD unit is disassembled, you will see PCB at the bottom. Near the front center of PCB, it has two chips labelled as '2072 JRC' which is responsible to detect low audio, and outputs bilevel OFF signal. According to datasheet, pin 6 is OFF when level is low.

What I did is, traced the pin 6 and noticed the bilevel was used to switch between AUX and DISC in LSI. Since I never use my DVD anyway, I simply grounded the pin 6 but if DVD was to be used it would be bringing the 6 and ground wires out externally and installing an ON/OFF switch. __ Alternately, I could have tap out Audio R and L (pin 8 and 16) from wiring harness in the back but when I did that I was not able to control(increase) AUX volume for some reason. __ Good Luck to you.