New Stereo for Old Truck


Old 12-26-11, 11:48 AM
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Join Date: Apr 2011
Location: USA
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New Stereo for Old Truck

I just got a new stereo for my 1991 GMC Sierra. I have never installed a care stereo, so excuse my ignorance.

I found the following information alleged to be in regard to my factory installed radio...

1991 GMC Sierra C1500 Car Stereo Wiring Diagram

Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

I just removed my old radio and there are only 6 wires. The information above suggestes there should be 13 differnt wires. What am I missing? I realize my infomration is limited, but any help would be appreciated.

I can provide a picture if that will help.

Thank you
Old 12-26-11, 01:15 PM
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Join Date: Mar 2003
Location: NC, USA
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Yes, often the radio or the car's wiring harness may have a different number of wires. Your existing/old radio probably has + & - to power the radio and a + & - for a left and right speaker which is about as simple as you can get. If the existing radio is not the OEM radio you'll have to look in the hole to see if you can find the other vehicle wires.

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