My sc400 95 has a stock premium head unit. I have a working nak amp in the trunk, 12 disk changer. My understanding is that my system is pioneer and not the nak system b/c the nak system has a nak hu (even though i have a nak amp). If this is the case should their be a sub amp powering my sub (pioneer)? Or should the sub be powered by the nak amp? Needless to say..my sub is getting no juice and the nak amp checks out.

 

It looks from the diagrams that all three 1995 SC400 audio systems have a separate subwoofer amp. Here are the diagrams from ARRC.

 

If you have a Pioneer H/U and a Nak amp, that means the previous owner must have done a mod of some sort. Are you sure it's a Nak amp in the back? They are two different sizes.

 

Positive. I've removed it and even replaced it with another used nak amp.

 

If you have a Nak amp in the back (I still don't know why the previous owner didn't install a Nak H/U) the woofer output comes directly out of the amp. The Pioneer systems have a separate amp for the woofer. BUT, I don't know if the Pioneer H/U would put out the proper signal for the woofer output. Have you tried any speaker lying around, maybe the woofer itself is fried and if yes, I would get a Nak H/U. They are on e-bay.

 

So a nak Hu would be plug and play? There are no wiring differences?

 

No. Which is why it's so confusing that the previous owner would go through the trouble of rewiring the trunk for the amp(it's not the same for the amps either) and not the H/U. Both H/U's have four plugs, two are the same, two are different. I removed the pioneer and installed a Nak system by downloading and printing both wiring schematics (they are on these forums) and just changing the appropriate wires. It's not hard as long as you make sure to cross off each wire done on both schematics as you're working.
FYI- If you want to increase the power on your woofer on the cheap, I went to some pick a part places, removed the Nak woofers from a few cars, then got some of the pioneer woofer amps from some LS400's, wired the Nak amp output into the pioneer amps and they drive three woofers in my trunk.
Speakers-$8.00 a piece
Pioneer woofer amps-$7.00 a piece
It takes some wiring but I love the extra power for little money