I have an mtx amplifier. it worked for a while then it just cut out, still turns on, no blown fuses, no smoke or funny smell, speakers work. what could be wrong with it

Looking at alot of the unsolved FixYa problems - I can see alot of "My amplifier is going into protect mode - How do I fix it?"

There is no catch all or simple answer. Troubleshooting steps must be taken to determine what is causing the problem.

It is one of 3 things....

1. Impedence under rated value or Thermal Protection.
2. Short to ground in wiring.
3. Internal Component Failure.


One of the more confusing things with a car stereo can be when the amplifier goes into protection mode. One minute it's working and the next minute it's not. Here's a brief troubleshooting method that will hopefully help you if your amplifiers ever go into protection.

1. Try to determine the cause. Amps can go into protection mode for several reasons. Knowing what happened before it cut out can help determine how to fix it.
Did the amp not work as soon as it was turned on?
Did it happen after blasting for hours (may be thermal overload and it needs to cool)?
Did it cut out after you hit a bump (a wire connection may have come loose)?

2. Tear it down. Get the amp down to it's most basic state. Remove all of the speaker wiring and RCA wiring and leave only the power, ground and remote leads connected. If you still have a problem in this state then either your amp is defective or you may have an installation problem such as the amp touching metal.

Remember that an amplifier should only be connected to the vehicle through the power and ground terminals. Mounting the amplifier to the metal of the vehicle, including putting the mounting screws into metal, can cause problems for your amplifier.

Always mount the amplifier to a non-conductive surface. An easy way to accomplish this is to mount the amplifier to a wood board and then mount the board to the vehicle.

3. If the amp is OK in this torn down state keep adding the other wires back on until you find what causes the problem.
Add the RCA cables first.
Then add the speaker wires one at a time.
If the speaker wires cause the problem then they are probably touching metal or have a blown voicecoil.
Check to make sure that a speaker wire isn't being pinched somewhere between the amp and the speaker.
Also check that the speaker wire or speaker terminals aren't touching the vehicle metal near the speaker opening.
Rear decks and door panels can easily touch unprotected speaker terminals if not properly installed.

If the problem starts occuring when you connect the subwoofer wires to the amplifier you may have your subwoofers wired at too low an impedence. First check the spec's on your amplifier to make sure what kind of loads it is stable under. Then check the wiring configuration to make sure that your load is not too low:

If you believe your amplifier is defective contact the manufacturer first. Many have flat repair rates that are very affordable and cover parts and labor.

However local repair shops may be cheaper if it is just a small repair.

Compare the manufacturer's repair rate to that of a local shop. If you don't know the reputation of the local shop it may be better to send it to the manufacturer who will have working knowledge of the amp and parts readily available.

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