Amp going protect, only with engine on...

I have two amps. One is a Polk 5000.5 and the one I am having a problem with is a polk 2000.2.

I have both amps getting power from a 4 gauge dist block that goes to the perko. The perko has two batteries feeding it and was on the "both" setting.

Now today I took the boat out to get warmed up before an oil change and I was checking out the stereo and the 2000.2 amp (that goes to a single WS 485) was cycling into protect mode when the volume was raised. The other amp was powering everything else with no problems..

Now the weird thing. I brought the boat home and checked on it and with the boat off and at the same volume as before it does not go into protect.

Is this an issue with the perko switch or alt or what?

All my electronics go straight to the perko and both batteries have their grounds going to the "grounding post" in the engine bay. Any ideas?

What is a 4ga block?

What model "perko" do you have and which terminal does the amp's trunk line terminate to?

Are the batteries' ground cables connecting directly to the engine block or some remote grounding post? If the later, what gauge is the main ground going from the grounding post to the block?

Whats the battery voltage at the amp's terminals?

What is the amp's cross-over filter set to?

Whats the cross-over frequency set to?

approximately, where is the gain set at?

Originally Posted by chpthril

What is a 4ga block?

What model "perko" do you have and which terminal does the amp's trunk line terminate to?

Are the batteries' ground cables connecting directly to the engine block or some remote grounding post? If the later, what gauge is the main ground going from the grounding post to the block?

Whats the battery voltage at the amp's terminals?

What is the amp's cross-over filter set to?

Whats the cross-over frequency set to?

approximately, where is the gain set at?

1. 4 ga wire goes to a Y connecteion where 2 4ga wires come out to go to each amp.

2. Not sure what model but the amps line goes to the common post on the perko.

3. Batteries are grounded to a metal terminal where the main ground from the engine. 4ga

4. Not sure

5. Full?

6. When i adjusted the gain up and down it was still cyceling protect

1) 4ga feeding both amps could be a little small without knowing total length. What size cable and length is the cable from the switch to each battery B+? What size is the trunk line feeding the amps and where is it terminating?

2) thats good

3) 4ga for the main boat ground seems a tad light, but wont effect the amps of they are wired directly to the battery

4) probably more important when the amp does go in to protect mode.

5) Needs to be in Hi-Pass

6) need to set using a common method.

Ohm'ing the speaker circuit to see what its nominal impedance is, as well as testing to see of the speaker leads are shorted to the tower would be the next steps.

1. From switch to battery is roughly 3-4' of 4ga. From amps to switch is 4ga and probably 8' length.

5. Ok ill try that.

6. Whats the common method?


Thank you for spending your time trying to help me. I truly appreciate it.

Any reason why it will work in my garage but not on the lake? Seems strange

At first glance, it would seem improbable that the amplifier would go into the protect mode with more voltage rather than less voltage.
A few possibilities no matter how remote are:
A misdiagnosis.
A defective amplifier.
Bad alternator regulation with too much voltage causing one amplifier with a more sensitive threshold to sense 'over-voltage'.
A bad ground causing another component to syphon off voltage or causing a DC offset on the RCA/ground.
Another installation flaw in the system. Primary B+ and ground, remote turn-on, RCA 'above' ground, or output load.
Bridged incorrectly.
You can use two basic methods for diagnosis. Substitution and isolation. Or, measurement.
Measurement of a static voltage won't tell you much as the load of a meter is almost non-existent. However, parallel voltage measurement when under load and just as the amplifier goes into protect will be more revealing.

Btw, bridging that 2-channel amplifier to a fullrange speaker has got to sound absolutlely awful. Unlike a bridged Wetsounds Syn2 or JL Audio HD750/1 monoblock you have no method of summing the left and right signals other than at the speaker's voice coils. Fine for a subwoofer but not a fullrange application.