Question about Rockford Fosgate Punch 401S Car Audio Amplifier

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Amp over heating

After about 15-20 minutes of my amp being on, it cuts out even at low volumes. Is there anything i can do to stop this from happening?

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  • ronnieyannon Apr 22, 2009

    i think I have my subwoofers wired wrong to the amp. Here's how there wired: sub 1, positive of the sub into the 1st positive channel on the amp and negative of the sub into the 1st negative channel. The same goes for my other channel on the amp. My amp is stable 2 ohm and 4 ohm. I have svc 4 ohm subs. What load does this give me? The amp is bridgeable. And how would you wire the speakers to the amp?



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There are only 3 reasons this could happen. First, faulty components in the amplifier.

Second, and far more likely, is that the impedance of the speaker load is lower than the amp is designed for. If you are connecting (for each channel) the speaker + to other speaker + terminals and then to the amp, as well as connecting the speaker - terminals to each other and then to the amp, assuming all speakers have the same impedance, your load impedance is speaker impedance divided by number of speakers. Make sure your amp can handle that load and change it if it can't or you will fry it.

Third is if you connect speaker + to amp + and then speaker and amp - terminals to the car chassis. This is shorting part of your amp and will destroy it. Neither the - or + terminals should contact the chassis.

Posted on Apr 22, 2009

  • rjivaro Apr 23, 2009

    It sounds like you are saying you have 2 subs and each sub is connected to its own channel on the amp. With 4 ohm speakers this would give you a 4 ohm load on each amplifier. If you connected both to the same channel you would have speaker impedance divided by number of speakers = 4/2=2 ohms seen by that channel. If you run bridged, each amp sees half of the impedance of the speakers, so you could only run 1 of your subs because the amps would see 2 ohms each.

    Since you are running 2 subs, one in each channel, the amp must be set for stereo (or more properly, 2 channel) operation. Do not use it in bridged mode and make sure your switches are set correctly.

    I am not familiar with that amp in particular so I can only provide general suggestions. Does the mfr recommend a cooling fan on the amp? Have you used an ohm meter to check for shorts to the chassis? Sometimes a wire gets pinched or punctured or a strand of wire is hanging loose and touching something it shouldn't. Have you used an ohmmeter to verify that at the amplifier end of your speaker wires you measure 4 ohms (+/- 1 ohm or so)?

    Almost, if not all of the current car amps use MOSFET transistors which I have found to be subject to leakage which leads very quickly to heat related failures. Usually that leakage grows over time, but it can happen even in a new amp or even with new transistors. After making sure that everything is wired correctly and the switches are correct and there are no shorts and no fan is required beyond what may be built in, if you still have the heat and shutdown problem the amp requires service.



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