Adding an AUX input to a factory radio

**ParrotSquawk** · 05-29-2006, 01:37 PM

I am in the process of adding an AUX input to my older ('95) factory radio that came with a CD changer in order to use my Sirius PNP radio.

I am using the diagram athttp://www.mbca.org/northtexas/audio_systems.htm. This diagram uses a switch, something I want to avoid.

Is there a way to use the ground for the Sirius radio to switch the factory radio from CD changer to AUX input, using a relay instead of a DPDT switch?

I have attached a pretty extensive wiring diagram if more information is needed.

Thanks.

Michael in FL

**Jahntassa** · 05-29-2006, 05:34 PM

You can put a relay in there, but you'll still need a switch to trigger it. There's nothing in the Sirius radios (any of them, as far as I know) that has an external 'on' output that would allow it to automatically trigger the relay on.

**Vinister** · 05-29-2006, 05:39 PM

Doesn't your unit still have a tape deck in it?

If you open it up, find where the signal from the tape mech goes into the preamp section of the deck. Feed your aux signal into there instead. In some headunits you'll have to stick a tape in there for it to work, but then you can keep your CD changer and tape seperate without using a switch.

**ParrotSquawk** · 05-29-2006, 09:27 PM

Originally Posted by Jahntassa

You can put a relay in there, but you'll still need a switch to trigger it. There's nothing in the Sirius radios (any of them, as far as I know) that has an external 'on' output that would allow it to automatically trigger the relay on.

Let's see if I can explain this clearer...
When the radio is on, +12vdc goes INTO the PNP then out again, running to ground. This POWER goes to GND. With me so far?

BUT!!! GND is just power AFTER it's used, right? I use the POWER leaving from the PNP to operate the relay (you can think of it as GND, but until it hits GND it can still power things!)

GND is what I would use to trigger the relay. GND going INTO the relay IS power (the relay is in SERIES with the power FROM the PNP.)

If there is no POWER via the GND (Radio off,) relay stays closed and CD functions as normal. Power up the unit, the POWER via GND OPENS the relay, switching signal source from the CD to the PNP

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Originally Posted by Vinister

Doesn't your unit still have a tape deck in it?

If you open it up, find where the signal from the tape mech goes into the preamp section of the deck. Feed your aux signal into there instead. In some headunits you'll have to stick a tape in there for it to work, but then you can keep your CD changer and tape seperate without using a switch.

Well..it DOES have a tape unit but I am not gonna open it up nor trust anyone else to do it :"it's old equipment and we aren't liable if we break it because its not a factory mod...yadda yadda"