Problems wiring amp to stock HU

[astrat16]

My sister has a 98 Limited and her front speakers are blown so Im replacing just the woofer with a coaxial speaker run off a after market amp, i have everything wired properly so the amp powers on when the the ignition is in the ACC/On position however i cant seem to get a signal from the HU to the amp.
I'm using a hi-low converter for the audio feed.
I hooked up the RF+ from the amp to the RF+ coming out of the back of the stock HU
Now i hooked up the RF- from the amp to the RF- coming from the stock auxillary amp because there is no RF- feed coming out of the stock HU

Am i doing this right? I've never had a problem like this before

Thanks in advance

 

[snowbrdr033]

I assume you also wired up the remote wire from the HU to the amp?

 

[ChipG]

Polarity problems

Sounds to me like a polarity issue. Find the RF positive & negative and swap them. Some line out converters wont work unless all the wires are in the correct polarity.