stereo issues

I've got one strange issue left with my stereo install that I have not run into before, and im hoping someone can shed some light on it.

The stereo plays fine with the motor off, but when the motor is on, the subs wont play (or they will cut in and out).

I've got a 120A high output alt, runnign to 2 batteries via a perko switch. Bat 1 is the boat, bat 2 is dedicated to the stereo. 3 amps are connected to Bat 2 with 3 60A inline fuses. The other two play just fine (one of the amps is 1000w ppi running my nvs's).

I checked the voltage at the sub amp and everything looks fine (remote lead too). I tried running in the rear inputs into the sub amp instead of the sub out to make sure it wasnt the output of the deck with no change in how it works, so im pretty certain something about the amp cannot draw enough current.

Each amp runs 8Guage power/ground, and again, works fine with the engine off.

Any ideas?

What if you disconnected the other two amplifiers such that you're only running the sub. Then repeat the test. That would eliminate a power starvation problem. This could be accomplished by disconnecting the remote feeds on the other two amps.

I wouldn't expect power starvation to be a problem.

Does it do it while the engine is at Idle, or only while underway? I'm wondering if it's a vibration/loose connection problem. This could be anywhere. On the power side, on the output side, a cold socket inside the amp. A bad fuse (unlikely.)

(Message edited by yosquire on April 23, 2006)

Ill try just running just the sub. It does it at idle. if you have the boat ideling, the subs wont play, turn the engine off, and they kick on.

You may want to check the voltage at the batts, your charge system may be over charging and the amp is going into protection. Any thing over 15 volts may shut down that amp.

After pondering a little while longer...

Try disconnecting the alternator -- Disconnect the exciter wire, or if it's self exciting, disconnect the charging wire.

This test doesn't prove anything directly, but it would tell you if the Alternator is contributing to the problem. Perhaps from there you'll have some more ideas as to which way to go to further the diagnoses.

ill give that a try, I have been using that alt for over a year now. I can also check the volt coming off the alt right?