94 buick wiring?

[B.dubja]

Am throwing an old Alpine CDA9856 into my daughters 1994 Buick Park Ave. The car wiring harness has 4 plugs. The front speaker plug, back speaker plug, power/ignition/antenna/illum/ground plug, and a fourth(?). SO, I am wondering what to do with the fourth plug cuz the dimmer doesn't work for the radio or heat controls(only with the factory radio does it work).

If it matters, it has a Concert Sound II. Speakers in the front doors and rear package tray.

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[RKaudioking]

You may have to get a radio interface for the aftermarket radio so the vehicle can maintain its factory functions.

 

[CrossoverOre 10+ year member]

if you used an interface harness make sure you are connected to the orange wire for the illumination of the aftermarket deck. If the factory deck operated the heater control illumination you may have to plug the factory on back in and use a meter to determine which wire you will have to just to make it work again.

 

[Side Show 10+ year member]

fit the deck in the glovebox, and leave the original one fitted, so you can still use those functions. (also good idea to deter thiefs ect)