i bought stereo cable and connector so I can hook up my phone/mp3 player and the darn thing plays it in mono ?
am I doing something wrong?

 

your phone puts out a mono signal. I know because my phone does too but yet my ipod it sounds fine.

 

I second that. You need the right cable for your phone too. Not all phone manufactures are the same. The hole size usually is, but there is different spacing on the sections of the plug.

Do you have headphones for your phone? if you do and they work stereo then look at the plugs side by side and see if they are spaced the same. You could try pulling the plug out just a hair and see if the other channel comes on.

 

Mine iPhone use to play in stereo through aux but now it's mono. I believe something is screwy with the head unit after trying different combinations and concluding it's not the cable or the phone.

 

try plugging in something else to the system (using the same cable) that you think plays stereo output... if it still doesn't work then you have a problem with the cables you purchased just like mentioned on the other posts... it could also be a problem with the radio but I doubt it... which system do you have? is it the stock radio? if so, is it RES, REQ?

 

Try pushing the connector in just a little bit further? that extra 1/16th of an inch can mean the difference betwix mono and stereo