Common Car Amplifier Problems and Solutions


Here at Sonic Electronix, we sell our fair share of amplifiers- among everything else car audio, and one thing you learn very quickly in this industry is that a lot of people fear (return) what they can't (improperly) install. So we're here to help.


Read below for suggestions on how you can fix common car amplifier problems!

* These suggestions are not definitive, and attempting repair/troubleshooting should always be done by a professional.



Many car amplifier problems are incorrectly diagnosed and returned because of incorrect hookup. 


Sometimes the amp itself really is at fault, but not often. If it is, read this.



Information sourced from: https://techlore.com/article/common-car-amplifier-problems-and-solutions

Problem: Amplifier does not turn on


Rule number one in amplifier hook up is to make sure the amplfier has a good ground. This means that it is secured to bare metal that is clean, rust-free, and tight.

Is the remote wire hooked up? Be sure it is, and that it is hooked up to the blue wire w/white stripe coming from the head unit, NOT the solid blue wire.

After that point, if the problem still exists, you're probably looking at bad parts in the PSU (power supply unit). The majority of the time, it's because mosfets are blown. It is never a bad idea to try hooking up the amplifier in a different car or taking it in to be tested just to be sure. Sometimes you can open the amp up and find physically fried components. For space constraints, I'll leave it at that.


Problem: Amplifier goes into protect


This can be caused by too low of an impedance from the way the speakers are wired, and sometimes a poor charging system (if the amp goes into protect when the volume is turned up).

Otherwise, it's likely that the output transistors failed. That's the most common cause for an amplifier to go into protection.
With no power applied to the amp, grab a multimeter, set it to ohms, and measure the
resistance between the output transistors terminals. You should
find none that have anything close to zero ohms between any of the
terminals. If you find one or more that read ~0 ohms between
therminals, they need to be removed from the circuit and checked. If
you have several in parallel, it may seem as though the entire group shorted, but generally one fails and the others are OK. Of course, when
you have one defective transistor in a group of parallel transistors,
you must replace all of the transistors in that group.
Open or broken emitter resistors can cause an amp to go into protect. If you
don't find any shorted outputs, make sure there are no broken terminals
on the emitter resistors


Problem: Amplifier is getting very hot/shutting down


This is normally a result of the gains/input sensitivity being set too high. In addition, a lower impedance than the amp is rated for can cause this problem (and in the case of a lower impedance, it can cause permanent damage). Make sure your gain isn't turned up all the way, and that there is at least a bit of dial space between the max and where it is currently set. Be sure the speakers are wired to an impedance the amplifier can handle, and that the speakers are in good working order.

If the above have been met and the amplifier is still overheating, the best thing to do is add external cooling fans. PC fans work great, and I suggest getting the 3-5" models. They can be hard wired to the car's electrical system and a simple switch can be wired inline to turn them on and off.


Problem: Amplifier's volume turns down

Many new amplifiers have protection circuitry that will limit the volume if they begin to get too hot. In this case, you would want to refer to the above problem for the solution.



Problem: Amplifier keeps blowing fuses

This is usually caused by shorted output devices or power supply
rectifiers. I'll refer you to the solution for the amplifier going into protect as it is basically the same thing, and is usually the root of the problem 95% of the time. Beyond that, it could be a shorted
filter cap, some sort of short across the power rails, some short across the output, or shorts across the primary,. And, let's not forget
loose hardware (any missing screws or nuts? A loose one under a pc
board can short out most anything.)


Problem: Amplifier has intermittent or no sound


This basically comes down to two troubleshooting steps:

  1. Try connecting a portable CD player to the RCA inputs (via headphone to RCA cable) and see if you get sound. If you do get sound, then the RCA cable from the head unit could be bad, or the head unit's RCA outputs could be fried or not turned on.
  2. Try hooking up a known-working speaker. If the speaker works, then
    chances are the ones you have are blown. Press down on the
    speaker cone of the likely blown speaker, and if it scratches, it's definitely bad.

Again, if that doesn't solve the problem, there is definitely a problem with the amplifier itself. Usually one of the output devices is to blame (seeing a consistency here? ;) ).


Problem: There is alternator whine or noise through the speakers


This is another classic example of a bad ground. You must have a good ground connection. If the ground has been checked and is not the problem, a noise suppresor might be necessary.



Thanks to Jexx at techlore.com for writing this information.

Disclaimer: Sonic Electronix is not liable for any damages resulting from the ownership of our products, nor will we uphold warranty for products incorrectly installed.