I put an aftermarket Alpine head unit in my H3. I accidentally ordered the Metra interface harness kit for a non-amplified system. I got everything to work except the sub woofer in the rear doesn't turn on. Does anyone know if there is a way to modify the harness or add a jumper wire to turn on the sub woofer in the rear when the radio is turned on?

I called Metra, but the guy on Tech support told me I need to buy a different interface kit ($136). I'd like to avoid this if possible.

Thanks for the help!

 

The Monsoon system amplifies the low voltage signal sent from the OEM head unit.
In order for the interface to work properly it will have to reduce the amplified power coming from your aftermarket radio.
The interface you purchased does NOT reduce the signal to low voltage. Therefor you are overpowering the Monsoon amplifier with a signal that it too powerful.

Purchase the correct interface and all of your speakers including the subwoofer will work.

 

Ebay the Metra you do not need after you replace it.