[edteach]

I have a 80 FB. It has a stock am fm radio. I put two new 6x9s in the rear and it works good. I took the 3.5s out in the front and hooked them up to This unit pictured. It is a two speaker system amp with MP3 decoder.The unit has three wires one ground one red fused to hook to a hot wire that does not go off with ignition, and a orange wire that hooks to a fused link that goes on and off with the ignition. It all works well until I start the eng and I am getting ignition noise. I called the vendor and was told to ground it out better. It is grounded out now. I put a test light on the ground and this the other end to pos and it lights up fine. Any ideas? I have resistor plugs.

 

[NOT A TA]

Jim, you need to isolate what's causing the noise.

If the noise stops during these steps you've found where the issue is.

First thing I'd do is make a couple jumper testing wires long enough to reach out the door to the battery. Connect one to the ground from the amp and connect or just have someone hold it on the - battery terminal. Then test before and after starting. Then repeat with the 12V power supply the same way to the + battery terminal. Then test with both the 12V power and 12V switched power direct to the battery + terminal by using the same test lead wire. (So you only need to make two test wires one for + and one for -.)

If you still have the noise with the amp connected to the battery directly. You'll need to isolate whether it's ignition noise or alternator noise. Remove the belt that turns the alternator and start the engine. If you still have the noise it's ignition related so come back here and post results. If you get to the point that it is probably ignition related we'll have questions for you to answer.

 

[ZumpTA]

This is going to come off as rude, apologies in advance.

Alternator whine is related to a bad or inadequate ground 99.999% of the time. Ignition circuit shielding could be an issue but that is extremely rare and more of a 50s & 60s car thing.

CHECK YOUR CHASSIS GROUND.

This is why I stressed GOOD ground in my last reply to you. That not only means good contact to metal, but also properly sized wire, and good chassis ground.

From my 71 Friebird, to my 80 Camaro, to my mid 80's camaro RS, late 80's IROC, mid 80s Lincoln and Grand Prix, mid 80s Nissan hardbody, 94, 96, and 99 Ford Ranger, current 93 Trans Am, 04 Toyota Tundra, and new 2018 Hyundai Elantra, and countless installs for friends, I HAVE NEVER HAD ALTERNATOR WHINE NOT RELATED TO GROUNDS.

I also never bought cheap amps. My current (bought in 1998 for $550) MTX Thunder 225HO (25wx2) actually puts down nearly 1,000w at .5 Ohm and is .25 Ohm stable. Used factory alternator with it in 94,96,99 Ranger and 93 Trans Am, never burned an alternator out with it either. It's power wire and ground is as thick as my thumb.

Of course, I also said NOT to hook into the cars electrical, so...

...run the 12v constant to the battery, not anywhere else.

...tie the 12v switched to the 12v constant with a toggle switch on it somewhere so you can turn it on and off.

...verify good ground at black wire AND your chassis.

That's a bottom shelf unit. Probably Chinese trash with an "American" sticker on it. I can tell by looking at it that it probably puts down less power than a $50 head unit. Want to know its true power? Multiply its fuse rating by 12 then 0.60. AT BEST, thats its true output, and 60% efficiency is probably being kind.

You can add resistors which suck power. You can try sheilding. You can do a bunch of things that are not required if the wiring is correct.

So, again, DO NOT TIE INTO THE VEHICLES ELECTRICAL. Professionals never install amps, crossovers, eq's, etc. Into the vehicles electrical no matter how tiny it may be or how little power consumption it has. Guess why. Sure the head unit is tied in and normally with an installation harness so factory wires are not cut or altered.

You can use the same constant 12v source for both the power and turn-on on that thing. Just splice the two together at the end and install a switch inline with the orange wire as previously stated.

So, red wire from battery to 12V input on amp. Orange wire connected to red wire. Cut orange wire and add a toggle switch to it.

Do you have a radio? Seeing the inputs being a 3.5mm headphone type I assume you want to plug the amp into your phone?

If you have a cassette player, they make $10 cassette adapters that plug into your phone headphone port to play thru the tape deck. For $50 you could have a stereo with bluetooth and forget the wires. Either option is better than just some cheap amp, but if you insist on this amp, and splicing into your electrical then chasing grounds and ignition system isolation is going to be mandatory.

I agree with your vendor 100%. Of course, something that cheap might be defective and have a bad INTERNAL ground, but, good luck finding that or getting vendor to own it. We get what we pay for.

Good luck!

 

[edteach]

I have an AM FM standard 70s type radio no cassette. I pulled the constant wire off and it stopped the eng. noise. I am going to try to run a line to the battery tomorrow outside the car and see if that does it. If not I will then try a dedicated ground and so on. Thanks for the help. I am not looking for a high end sound. Just some tunes when the radio is out of range.

 

[ZumpTA]

When you pulled the constant wire, you cut power to the amp. The orange wire when powered opens a relay in the amp that allows the amp to power up from the red wire.

If the amp stayed powered on without the red wire and the noise went away, that's an issue. Stop now and return it and look into this: https://www.amazon.com/iSimple-IS31-Antenna-Modulator-Aftermarket/dp/B002U5XPBE

That $25 box plus an RCA-to-3.5MM phono adapter in my opinion is a better and cheaper solution. Not recommending that product, just showing a better way to get what you want.

Also, are both your radio AND that amp plugged into the same speakers? You can't do that.

...well, you can, but...

 

[NOT A TA]

It was my understanding from the OP that the 6 X 9's were hooked to the stock radio and the 3.5's were run off the new amp. As Tony mentioned don't hook both to the same speakers. Also as he mentioned if the amp works with the constant disconnected return the amp.

 

[edteach]

It was my understanding from the OP that the 6 X 9's were hooked to the stock radio and the 3.5's were run off the new amp. As Tony mentioned don't hook both to the same speakers. Also as he mentioned if the amp works with the constant disconnected return the amp.

This is correct. I ran an 18ga wire from the constant directly to the battery terminal and a neg to the neg battery side. This seemed to fix the issue.

 

[NOT A TA]

This is correct. I ran an 18ga wire from the constant directly to the battery terminal and a neg to the neg battery side. This seemed to fix the issue.

Cool, so wire it permanently that way. As Tony mentioned that's what most consider the "correct" way to wire it.