sony cdx gt710 head unit no sound

Hey guys, I recently purchased a used Sony CDX-GT710 head unit. I connected all the wiring correctly using a harness adapter. My problem is that itt does not seem to output sound through the stock speakers in the car. I plugged in a RCA cable and it seems that there is sound output through the pre amps, just not through the speaker harness. The unit replaced a Sony CA-860X, which worked fine, so I know the speakers in the car, etc work. Is there a setting on this unit that turns on or off the internal amp? Worst case I'll pick up a 4 channel amp and use the pre amps to drive my speakers. Any input is appreciated. Thank you!

I had to bypass the factory amp in this vehicle, so i have the speaker outputs from the harness directly connected to teh speakers in the car. the old sony unit uses the same pin out and harness configuration, so i know the set up worked on my old head unit. i'm never going to buy a used head unit again!

how old was the sony HU that you replaced? i ask because if it was really old then it might not have the protection features of a new deck, so it still would be possible to have a speaker problem and your old deck play fine while the new one might be detecting a problem. just a thought.

The 710 may have a menu setting that will defeat the internal amplifier.  You may have to look through the menu for such an option.   You should be able to download the user manual from sony's website.

the old unit was about 5 years old or so. i originally thought of the internal amp too, but have not been able to find anything online or in the manaul for how to disable it. i've played with all the settings but havent been able to figure it out. help!

thats a good idea with testing one by one. i'll check it out this weekend. thanks!