Polk Amp turns on and then off

[toddrswenson]

Before anyone asks I don't know what model my polk amp is. I'll look tomorrow. I bought the boat used and the system has worked great until today. We were on the lake all day and all was fine and then all of the sudden the amp that powers the sub and non tower speakers quit working. I loaded the boat and turned it on when I got home. Everything was fine and then the amp cut off again after five minutes. I washed and waxed the boat and turned it on again and it worked for about five minutes. I assume it's going into some sort of protect mode. Does anyone have an idea of what might be causing the problem?

[Ewallace]

Power wires from the battery may need to be increased in size, or amp is getting to hot and you will need to install a fan or other device to keep them cool.

[toddrswenson]

I thought it might have over heated as well but its been working fine for a year and the cables look to be of
ample size. I let it cool down for two hours and powered it up and it did the same thing. Troubleshooting begins now. I have week long trip planned leaving Tuesday. Any help is appreciated.

[David Analog]

If you are going to own a boat that is stored an inconvenient time and distance from a shop then you must have a multimeter. It’s a small but essential investment. Decent quality for $20.
If the amplifier is shutting down before it has had a chance to get really hot then the issue could be low voltage. Measure across the amplifier primary power terminals while under load. Then measure the same at the battery terminals on the specific battery that is supplying the amplifier. Any difference in voltage is an indication of resistance and a bad connection. Also, make a hard physical check on all terminations including battery grounds.
Make sure that the battery supplying the amplifier is still good and that it is not isolated from the boat’s charging system in some way.
If you suspect it is a thermal issue then you could have one bad speaker. So in that case, either measure the DCR of each speaker individually looking for a discrepancy, or remove each speaker one at a time from the amplifier until the thermal sensitivity is removed.
If voltage is good but the amplifier still shuts down with a minimal or no load then that’s an indication of an internal amplifier problem.You can also measure the output impedance of each amplifier channel looking for a discrepancy.
Prematurely replacing the amplifier could leave you with the same problem.
You don’t have much time for speculation. You have got to verify by either taking measurements or using manual isolation and/or substitution.

[toddrswenson]

I'm leaning towards a voltage problem I think. When I combine my batteries everything works well. I'm guessing I either have a bad battery or alternator. Looking into how to check the alternator out. If I check voltage at the battery when the boat is running shouldn't I have around 14 volts?

[David Analog]

The exact voltage will depend on the load and battery state also but you should read an immediate increase in voltage once you start the engine.

[MLA]

Sounds as if the amp is wired directly to a battery. This means no alternator contribution, unless the switch is on that battery or in the combined position. This would easily explain why is operates fine with the switch in the combine.

[Banffskiing]

The switching power supply inside the amplifier has a minimum voltage that it will continue to operate (IE safety). if it does not do it a low volume then that is almost certainly the prob.