Car Stereos: Thinking of putting a system in my 2002 VW Jetta 1.8T, monsoon speakers, vw jetta

Question
Hello Brian,
I have a 2002 VW Jetta 1.8T with the Monsoon equipment and where thinking of installing an alpine IDA-x100. I heard that in some VW's the radio is tied in to other components in the vehicle and can cause some major head aches if removed. I was thinking of using the monsoon speakers and amp since it sounds pretty good and adding and additional alpine amp to run a single 10 or 12 sub. What draw backs or concerns do you see with my plan, your advice and tips would be greatly appreciated.

Answer
Hi Ken,

You shouldn't have any problems removing the stock radio from your Jetta.  No other vehicle systems will be affected.  There are really only a few issues you'll need to be aware of:

First, your original Jetta radio is equipped with an anti-theft system.  If it's removed, then replaced, you'll have to enter a special code to make it work again.  The code should have been included with the original documentation that came with the vehicle. This won't cause any problems when installing the new head unit, but it might become an issue if you want to re-install the original head unit before selling the car.

Second, there's a wire in the VW radio plug that's connected to the OBD II diagnostic plug under the dash.  If you're using an adapter harness, this wire lines up with the "power antenna control" wire in the adapter.   It's important that this wire remains disconnected.  When connecting your new head unit through a Volkswagen wire harness adapter, the only wires that should be connected are the power, ground, illumination and speaker wires.  You should not connect to any blue, blue/stripe, or brown wires in the adapter harness.  If you do, this could potentially damage a mechanic's code reading equipment.  For this reason, many mechanics won't connect a code reader to a Volkswagen with an after-market head unit installed.  This could especially cause some problems if you're in an area that requires vehicle emissions testing.

Third, the Jetta uses an antenna amplifier to strengthen the signal from the roof-mounted AM/FM antenna.  The amplifier is activated with a voltage through the center conductor of the antenna cable.  If it's important that you get good radio reception with your new head unit (especially AM radio reception), you'll need to buy an antenna adapter that's made for activating the antenna amplifier. The Metra part number of the adapter is 40-VW53.

If you're happy with the sound quality of your Monsoon system, then there's no reason not to keep the stock speakers and amp.   You don't have to do anything special to integrate the new head unit; the factory system uses high-level inputs and a signal-sensing amp turn-on circuit, so it should work well enough with the new head unit in place of the factory one.

Hope this helps!

Brian