Question about MTX Thunder 421D Car Audio Amplifier

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Amp turns off when head unit is playing cds

I purchased a MTX TC2002 amp and wired it.It works great when using just the radio.When I change the source to CD, the amp shuts off.Any idea why? Thanks, James

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Re: Amp turns off when head unit is playing cds

Connect the remote turn on to the blue wire w/white stripe coming from the head unit, NOT the solid blue wire which is the antenna turn on.

Posted on Nov 02, 2006

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My MTX continues to draw power even when the key is not in the ignition. What can I do?

It sounds like you have constant 12volts applied to your remote turn on lead. The amplifier will have 3 connections for power:

1. 12volt constant
2. chassis ground
3. 12volt switched power - this wire should come directly from your head unit. It only sends 12 volts when the radio is on allowing to amp to power up only when the radio is on.

Dec 22, 2010 | MTX JackHammer JH600 Car Audio Amplifier

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I have a mtx thunder 421d. I've had it about 5 years,about a week ago it started going out from time to time. I checked my hot wire and fuses,they are ok.Now the amp stop working, and dont light up. Will...

If you have proof of purchase(invoice or receipt) showing the purchase date and you are still within the warranty period then yes it would be repaired by MTX under the warranty guidlines, and by the way MTX is great at customer service and they are great to work with(very fair)!!!!
Keep in mind that the seal on the bottom of the amp cannot be broken or that will void warranty coverage.
Give them a call, you will be glad you did!
800 225 5689 - MTX Customer Service & Amplifier Service Center
Good luck !

Jan 31, 2010 | MTX Thunder 421D Car Audio Amplifier

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If the amp produces no boom with no signal input cables connected, I'd suggest using an LOC.

Let me know if you have any other questions.

Sep 30, 2008 | MTX Thunder 3401 Car Audio Amplifier

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Mtx 1501D

if your power light is on then check your preamps (sub out from head-unit).Maybe you need to turn on that output thru head unit's audio menu.Also when using dual voice coils if you wire them out of phase there will be no output

Sep 16, 2008 | MTX Thunder 1501D Car Audio Amplifier

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MTX TC2002 amplifier has a noisy gain control

Not really, other than sending it to MTX or an authorized repair shop.

Jul 11, 2008 | MTX TC2002 Car Audio Amplifier

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Cant figure out my car audio problems!!!!!

There are a couple of tests you can perform. I'd first recommend checking the shield ground. You'll need an ohm meter. The details can be found on the following page.

RCA shield ground test

You can also test the output with the multimeter. Set the multimeter to AC volts. If it's not an auto-ranging meter, set it to a voltage range of ~2v AC. Disconnect the RCA cables from the head unit. Touch one meter probe to the outer ring of the head unit's RCA jack. Touch the other probe to the metal contact in the center of the RCA jack. With the head unit near full volume and a clean signal source, you should read at least one volt on musical peaks. If you have a bass disc or a test tone disc (~60hz sine wave), use those.

May 04, 2008 | MTX Thunder 8302 Car Audio Amplifier

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Short Curcit?

the amp have an input harness? those can go bad, or maybe line level inputs are loose. If its not just a loose connection on one of the amps inputs (speaker, line, or power) leading to the circuit board( which could easily be soldered back to the corcuit board), than your looking at an integrated circuit problem- not easy to fix.

Feb 27, 2008 | MTX TC2002 Car Audio Amplifier

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No power

It sounds like your charging system may be causing the problem. The voltage may be too high or the stereo may be too sensitive to high voltage. You need to connect a voltmeter to your system to make sure it's not charging over 14.5v. A normal charging system wii charge at 13.5-13.8v.


Have someone connect a digital multimeter to the B+ and ground wires of the head unit. Have a passenger monitor the voltage while driving. If the head unit cuts out at the same voltage each time and the voltage isn't excessive, the head unit needs to be repaired. If the voltage goes up above ~14.5v, the charging system needs to be checked.

Oct 17, 2007 | Car Amplifiers

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