Noise problem from sound system

Hey guys

I have a 2 amps one is a Alpine and the other is a off brand but like 1200 watts.
The problem Im having is poping and cracking through the speakers. I have
1200 amp connected to front speakers and a subwoofer. I have the Alpine speakers connected to the rear 6x9 speakers. I have a Jenson Cd player
with a y splitter for the pre amp plugs going to the amps. The cracks and pops
seem to be comming when the engine is running and driving. I turned the
system on parked and not running for hour and half with just good music.
I bounced the rear end around a few times also for maybe a short or something
and no cracks or pops from system. Any tests I can do to narrow the problem
down. Im leaning towards the cheaper amp. Ive also have a electric fan and
Ive noticed when it kicks on there is a buss through the speakers from the
Fan also.

Thanks for the help.
Steve

I been on some short trips and made no noise except when the the electric
fan kicked on. I went on a longer trip and all of sudden had the popping and
cracking. Ill have to check out how close the pre amp cables are to the power
and check out my ground. Thanks for suggestions.

Steve