weird Electrical problems in my 86 RX7. HELP PLEASE!!!
 

So, I have had my 1986 Mazda RX7 for a couple months now and have fell in love with her. Started to do the mods and upgrades to the car and with this ended up putting in 2 12" inch mtx subs. The subs worked great for awhile and would really give you a headache when you turned it all the way up, which is what I was going for, which may surprise some of you. Anyways, one day I am out driving and when I put on my brakes my subwoofers shutoff then somewhat kick back on, but they are offbeat from one another giving of a really horrible bass sound. This happened during the day, but only somewhat happens during the daytime. Night time becomes another story in itself. When my headlights are on and I press my brakes my subwoofers always shutoff or go offbeat as well as my lights are dimming in my car. I have looked and looked for possibly a grounding problem and have not found one. Another weird instance is when I took my ground off my amp and turned on my stereo equipment and my amp kicked on giving some power to the subwoofers, which I am no genius but this should definately not have happened. I am wondering if my amp is fried and I should buy another one or if something else is causing this electrical mess in my car. I am stuck on what to do and would like help before I end up going and spending hundreds of dollars for a new amp when I quite possibly might not need a new one. Any help at all would be greatly appreciated. :)

-Waiting to get my car back to normal.....

Im probably guessing that your alternator is not giving enough power to power all the eqiuptment at the same time, espicially at night time since the head lights and tail lights alone draw alot of power. With the Subs on, the lights doesnt have enough amps to draw from since the amplifier for the sub is taking most of the power, which is why your lights dim.

First thing you should do when installing any amp with 300+ is to install a capacitor, but the best option is to get a more powerful alternator. Only option (Im guessing) is the FD alternator which puts out 100 amp, which is way more then the wimpy 70amp the FC puts out.

Plain and simple, your system is using too much power, and the alternator cant make that much power to supply it. If you keep on driving it like that, you are going to need a new alternator pretty soon.

you definately need a capacitor at least a 1 farad cap .try this before purchasinig a new /bigger alt.it might be more cost effective and solve your problem.i use to have the dimming of the cluster lightsbefore i intaled a digital 1.5 farad cap.75 dollars.i have 2 amps 1 /400 watts the other 360 watts.havent had any problems since.oh yeah make sure you have at least an 80 agu fuse on your power lead cause when you crank upthe bass you dont wanna be blowing fuses all the time. good luck

buy a capacitor