MMCS and new amp Problem



My car has a MMCS system and I am adding an amp and High to Low Level Converter to change the original speaker wire to RCA plugs for the amp.

From the amp there is new speaker wire to the speakers so no original wire from the amp to speakers.

Orignal speaker wire has been cut and routed to the High to Low Level Converter.
Original speaker wire were cut and re routed, Rears just down below the rear door hing behind the seat belt,
and the fronts just where the door loom comes through the door hing beofre the plug.

Amp has power, yes
I only have the R/H speakers installed at the moment.

PROBLEM 1 - (I havn’t had much time to fault find yet.)
OK When I first put power on there was like this horrable pulsing noise WA WA WA WA noise

When you wriggle the loom behind the radio it goes away! Well after it makes some crackling sounds first.

Problem 2 – Both Front and rear R/H speakers are working, move the balance all the way to the rear and both stay on?
Move the balance all the way to the front and they both go off and another horrible noise a little bit like the first one but more of a “ti” pulsing sound than a “wa”.
I can make the noise lauder by turning the amp gain up but turning the volume knob does nothing.

I’m thinking there is an exposed wire somewhere behind the radio?
Is there a factory cross over box somewhere?



Sounds like something isn't earthed correctly ?


I had some time tonight and found the problem, looks like someone has already played with the spearker wires and left some small bits exposed which created my problems, I rewired the speaker wire now its perfect :D




1 AYC Bar
First Name
1999 Legnum Type S
lol man looks like some hack had a go before you! Good to see it all tidy :D That pic affirms my hatred of cheap electrical tape!


Leaving Skid Marks
First Name
purple legnum
can anyone give any sort of insight into how one would go adding an amp to upgrade the mmcs stereo. I really want to keep the mmcs but the stock stereo is really weak and i love to listen to music in the car.

I have no clue about car stereos other then the head unit + 4 6 inch system I installed in my first car about 10 years ago. I would love to do the job myself if possible. Im afraid that If I go to a car stereo place they will just take me for a ride and sell me what they want to sell not what I want and can afford.

Looking to spend <$600 all up.

Hoping to do something like MMCS head unit> high level amp > front splits + sub and possibly run the back 6inch from the stock mmcs head unit.

am I thinking correctly? what bits should I be looking for and where should I look? Sorry to highjack this thread but I dont seem to have the rights to make my own!
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