O.E HU pwr wire vs amp

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Installed in my 2000 neon for the past 8 months has been the pioneer F500BT. This was hard wired to the pink power wire of the stock radio harness and also powered by a cigarette lighter style DC charge.

http://www.pioneerelectronics.com/Stati ... al0714.pdf

I recently purchased the attachment to the F500BT unit which is the ND-G500 external amp. Its purpose is to allow the audio from the F500BT to come through all the speakers while upgrading the output of the factory speakers 22wx4. The harness of this unit; ND-500 I connected the power wire also to the pink wire of the stock radio harness and connected all the speaker wires to said one.

http://www.pioneerelectronics.com/PUSA/ ... 00.Support
The problem is: when I reconnect the stock radio, my gps only comes on if the power button of the stock radio is unpressed. (pressing in and out on volume control) also when the button is unpressed for the gps to come on; the stock radio flashes on and off appearing like a short is in the connection which their is none.

Can an external amp be wired to this radio battery wire?
Pink Wire..

http://www.dertycustoms.com/seats/5.jpg