The left speakers in the front and rear of my 1991 buick century are not working, the right speakers work fine. I checked the connection to the speakers and they are connected fine. What do not know how to do is how to check the connection of the speakers to the radio head unit. Could you please help me with this?

Buick Century Audio - Radio, Speaker, Subwoofer, Stereo

www.crutchfield.com/.../Buick-Century-Stereos-...
Crutchfield CorporationFind car audio products that work with your Buick Century ... your Century, 2005 Buick Century Sedan, 2004 Buick Century Sedan, 2003 Buick ... Here are stereos, speakers, and subwoofers that work with the Buick Century ... Rear Speakers .... time to talk to you through installation snags, troubleshooting, or everyday use.

Antennae wire and other wires for the stock stereo are listed below:
1995 Buick LeSabre Stock Radio Wiring Diagram
Car Radio Constant 12V+ Wire: Orange
Car Radio Ignition Switched 12V+ Wire: Yellow
Car Radio Ground Wire: Black/White
Stereo Radio Illumination Wire: Gray/Black
Stereo Radio Dimmer Wire: Brown/White
Stereo Radio Antenna Trigger Wire: Dark Green
Stereo Radio Amplifier Trigger Wire: N/A
Front Speakers Size: 5 1/4? Speakers
Front Speakers Location: Doors
Left Front Speaker Wire (+): Tan
Left Front Speaker Wire (-): Gray
Right Front Speaker Wire (+): Light Green
Right Front Speaker Wire (-): Dark Green
Rear Speakers Size: 6? x 9? Speakers
Rear Speakers Location: Rear Deck
Left Rear Speaker Wire (+): Brown
Left Rear Speaker Wire (-): Yellow
Right Rear Speaker Wire (+): Dark Blue
Right Rear Speaker Wire (-): Light Blue

Check the front window solenoid, and the window switches to see if your getting power to, and out of the switchs.

For 2001 Buick Century Car Radio Stereo Audio Wiring Diagram...

Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: Brown
Car Stereo Antenna Trigger: Pink
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


Hope helps (remember to rate this answer).

check for voltage going to the socket, then check grounds

No Diagram. You either need brake work or have a blocked rubber hose or caliper,on the left side and all the braking is taking place on the right. Very old vehicle,so expect these issues.

try 2 new bulbs

It is the blinker bulb more than likely. When one burns out it does this so you know to replace. Just open up the trunk and remove assembly from inside trunk remove bulb and replace. Should fix it.

check wire contacts in socket. If they are melted change the socket
It can be removed easily just unplug the wires.
I have replaced both front sockets on my 1999 Buick Century.
Hope this helps.
Ron

Motor which runs when u press the switch has loosened connections or is not functioning
Get it checked