hey my sub seems to be causing the headlights and interior lights to dim when it hits, my question is it because of the alt or the battery? so I know which one to replace. Im running 2 amps 300 rms to a MTX 12 and 120 to 4 6x8's

It is because you are putting too much strain on your alternator. Your alternator does what it can until it is exceeded in which case then it pulls from your alternator and battery. If your battery drains which takes no time at all, then devices will start dimming and not functioning properly. Replacing your battery will not help unless you go big with something that is made to do stereo stuff like Kinetik or something along those lines. You could do that or you can upgrade your alternator from Iraggi Alternators or Ohio Generator. But before you do all that, try doing the big three first. Upgrade your ground wire from your battery to 1/0 ga to the chassis. Upgrade your alternator power wire from the alternator to the battery to 1/0 ga. And lastly upgrade your engine ground wire to 1/0 from the engine to the chassis. You should see some decent results. If that does not kill the problem, consider using the band aid approach and get a capacitor. That should help alot. But don't skimp out on it. Buy a good one. Look to spend around 100 dollars for one farad. Oh and next time try a search. Let me know what you do and how it works out.

I second the "big 3" change... do a quick search and you'll find some good write ups.

Remember you do not have to change the wires. Just upgrade them. You can leave the existing wires in there just add the new ones on top of them.

I upgraded my big three and my factory alt and Duralast Gold battery handles a 1200 watt rms sub amp fine.

Also...I would recommend upgrade the body/frame ground straps

Another possibility is you choice of ground point for the amps. I would start there as it is the easiest. At only 500 watts, your system shouldn't even begin to touch your electrical. Where are you grounding your amps, and with what size wire?

I have them grounded on the rear seat metal flap, im trying to figure out a better place to ground, and im using 4 ga wire

Do not ground the amp on the seats or the seat bolts...Find a nice area around the back quarter panel and scrape the paint off and put you a self taper in there on some good metal, or drill a hole and run a bolt through there and ground it that way. Make sure you are not drilling into anything though. Be careful for the gas tank. That very well might make the issue go away. Good call Aaron.

rear seat metal flap??? please make a new ground. That is a HORRIBLE GROUND.

Best ground is to the frame...drill a hole and run the wire there.

If you ground to the body. I'd suggest upgrading the ground straps below the vehicle and doing to big three.

You will be fine placing your ground in the floor to either side of the truck over the frame. The floor is welded directly to the frame anyways.

how about under one of the bolts that mount the rear seat to the floor?

Never mind I just reread that you said not to do that. When you say the rear quarter, do you mean somewhere behind the rear quarter panel?

If you're having trouble finding a good ground, there is no shame in going all the way back to the battery. It isn't really necessary in a truck, but I've gotten over a 1 volt increase in my Mustangs in doing so (unibody welds don't pass current very well).

my 98' is a body on frame chassis with ground straps...I'm not sure how the new models are made

my 98' is a body on frame chassis with ground straps...I'm not sure how the new models are made

I haven't even crawled under mine yet to look. I hope I can ground somewhere in the rear, just because I don't want to drill a second hole in the firewall. This is the first Ford I've ever found that doesn't have a huge unused firewall grommet/bushing in it.

Never mind I just reread that you said not to do that. When you say the rear quarter, do you mean somewhere behind the rear quarter panel?

Not behind the panel. Close to it. Pull back the carpet and make one. If you check under the truck it is right over the frame. And if you are real good with a DMM you can run a wire to the positive side of the battery and the other to the negative side of the battery and test the voltage when the car is running. What ever that voltage is, you then do not want to lose more than .2 volts of what it is. Take the black prong off of the battery and leave the red one on it and get a jumper or something that can reach all the way to the back of the truck. Put the jumper where you want to ground it. If your battery is saying 13.4 while running then you should get the ground in the back to 13.4 also, if it reads different then move the ground to a new location. You can use it if it reads 13.2, but any lower will introduce ground loops. Hope you follow what I am saying.