btaylor

I have a 1999 Honda Accord with the factory head unit. I bought a MTX re-Q5 so that I could hook up some amps, JL Audio Slash v2 300-4v2 to power the interior speakers (alpine S types - 6.5" componet up front and 6x9" in the rear) and an Alpine MRP-M350 mono amp for my sub-Rockford Fosgate P2 DVC 4-ohm 12". I have it all wired up like the Crutchfield wiring guides for multiple amps show with a Rockford Fosgate 1 faret Capacitor. The system sounds great while the car isn't running but when I crank the car the volume is gone. You can hear music but only when you turn it up to the max. I have tryed re-grounding everything and making sure all the connections are tight but nothing has helped. Both amps are on. If they are on with the car off and on with the car running why does the volume cut out? What do i need to look for or do to make this thing work. Do I have a power loss problem or could something not be wired right? any suggestions would be appriciated. Thanks

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Dougw133

When you say with the car off? You mean key turned on or ACC? And then when the engine is running you have what sounds like "Un Amped" audio? If that is the case when the car is running check the amps and see if they are on. They should have a light. Sounds like a wiring issue/ground to me. I know you are confident that you installed correctly but....We have all made the smallest mistakes and cause major issues. Check that all connections are solid. I had an issue for months that clipped my amp at higher volumes. It turned out to be a spaker in my door was touching a positive lead to the body grounding it.

scatebase

If the amps are on when the car is on, it sounds like the MTX device might be losing power when the car is turned on. Check where it is getting power and remote turn on.

btaylor

Yeah when the motor is off and the ignition switch is in the on position the stereo works fine. As soon as I hit the starter and the motor is running the stereo sounds like it is un amp'd. You can hear the music but just barely and when I turn the stereo up as loud as it goes its only about 1/3 of the volume as when the car is off.

I just completed my sub box and installed the amp and sub. The rest of the system has been working fine for two months. Thats what is bothering me. The only thing I added was a power wire to the capacitor to power the sub amp and i tied the remote turn on wire into the other amp.

It all worked until i started the motor. So I thought maybe the ground was the problem so I have taken all the componets and grounded them together. Both amps, the capacitor, and the MTX unit are all grounded to the same place. I took sand paper and got all of the paint off of the grounding area but again the stereo works with the motor off and not when it's on.

The amps lights are on when the motor is on just like when the motor is off. I wouldn't think it was a power problem when they work with the car off. I test the volts and with motor off the battery is putting out 12.4 and when the motor is running its putting out 14.somthing so there is plenty of power.

What when i start the car is causing the amps to die? another thing is that while driving with the stereo on it will suddenly get full power and blow my ear drums out. Then it will cut back again. Its rea sparatic and doesn't always happen.

It has to be something small and I am just not familiar enough to catch it.

scatebase

Where is the remote turn on getting its source from?

Dougw133

Really sounds like the grounds to me...Or ground for that matter. Having all of your devices on one ground is asking a lot from that spot. Try to breakem' up a little. Maybe use to different spots. As always the grounds should be as short as possible.

btaylor

the remote turn on is coming from the MTX box. I had thought about running one from the radio remote spot and the other from the MTX. I will try the multiple grounds idea too. So is the ground really affected with the motor running?

scatebase

I made the attached image to hopefully clear up any confusion. Let me know if everything looks correct in there.
I have never used the MTX re-Q5; what is connected to it? is it just power, ground and speaker input with a remote out and rca out?

Attached Images

 

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btaylor

yeah that looks right. i had both amps hooked up to the cap but i took the JL amp off and it connects to the power wire before it goes into the cap. yeah the MTX has rca jacks coming out for the front, rear, and sub. all of the inputs i just spliced into the back of the stereo and it has the ground and switched power and constant power. i tried switching the two powers but it didn't make any difference.

scatebase

It seems weird because it works when the engine is off. You said the problem started when you hooked up the sub? Try to temporarily disconnect the remote turn on from the sub amp, and if everything elses starts to work, try shorting the remote turn on to the 12v on the amp. If that works, there is a problem with the remote turn on and you might need a relay.

Dont leave the remote shorted - it will kill your batt.

btaylor

yeah all worked fine before the current sub set up. i had my girlfriends sub hooked up to it with the same amp and all was fine. but i will go give the remote short a shot.

btaylor

well that looks to be the problem. the JL amp is rocking and when i plug the Alpine it cuts off. I guess i will try to run a wire from the HU's remote turn on point. that way they aren't both coming from the same source.

scatebase

Did you have the cap before also? That might be causing problems.

scatebase

The turn on lead probably cant handle turning on everything. You could connect the turn on lead to a relay that would connect 12v from the batt when the remote turn on is triggered.

btaylor

please explain to me more about the relay, where i could get one and how i should hook it up. that sounds like the best idea. thanks for the help

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