help with 98 4runner stereo upgrade

 I have a '98 4runner with the factory radio/cassette/cd with 6 speakers and a external amp thats mounted just below the radio. I'm installing a 2 chanel amp to drive a mtx truck box with 2 10" woofers,2 mid range, and 2 tweeters. Since my stereo does'nt have rca outputs,I'm using a line output converter to give me my low level rca outputs. I tied in to the speaker wires on the output side of the factory amp , but I don't have any audio on the right side. I'm using the black / yellow wires for the left and the red  / white wires for the right. I've checked all the connections, the rca cables, etc.  Could the right channel of the amp I'm adding be out, or the converter be faulty?doimakemymarkhere?

thanks for your reply jeff (at velocitymotorsport) . I think I have the double DIN player. This is probably a real lame question but how do I tell the difference between  a double or a single DIN player?doimakemymarkhere?

I tried swaping the RCA cords and yes the right side of the MTX speaker box works instead of the left. But I've triple checked my wire connections. I'm wondering if the line output converter that I got from crutchfields has a dead right  side. I've checked the continuity everywhere but  "thru" the line output converter. doimakemymarkhere?