[MK2Racer]

Intermittantly, when I try to accelerate at low rpm's (like crusing in 4th or 5th) my subwoofers will shut off. They work fine, and as I step on the gas, the "protect" light on the amp comes on and the subs go off, then after I let off the gas they come back on. It isnt a short, that I know of, becuase I can accelerate/decelerate hard, corner hard, go over bumps, etc and NEVER have a problem. Only when I hit the gas, usually in 5th, at low rpms (like 1000-1500), not while just running at that rpm. Any thoughts?

 

[Speed Racer]

Intermittantly, when I try to accelerate at low rpm's (like crusing in 4th or 5th) my subwoofers will shut off. They work fine, and as I step on the gas, the "protect" light on the amp comes on and the subs go off, then after I let off the gas they come back on. It isnt a short, that I know of, becuase I can accelerate/decelerate hard, corner hard, go over bumps, etc and NEVER have a problem. Only when I hit the gas, usually in 5th, at low rpms (like 1000-1500), not while just running at that rpm. Any thoughts?

Chances are good that you have a charging issue. The reason why your "protect" light comes on and the amp goes off is because your charging system isn't providing the amp with enough current to do its job.

One of two things is going on; either you have an alternator that's not charging adequately, you might have a bad voltage regulator but my guess is it's simply your battery. Your amp isn't getting enough from your electrical system to keep itself on, so your protect light comes on and the amp goes into a "stand by" state.

There is another possibility that your amp has issues, but I'd be willing to bet that the problem lies within the charging system.

Good luck.

 

[supra_toy]

What kind of subs and amp are you using? what gage wire? fuses? Are you running a cap? how old is the bat?

you could try using a cap...

will

 

[jbrody44]

I thinkn Stephen is on to it. When you hit the gas at that low of an RPM your charging system is not creating the current necessary to fire the ignition system and pump the subs. As a rule, I generally do not hit the gas at anything below 2000 rpm when in any given gear, I downshift first, then hit it. My 5M seems to be much less responsive under 2000 rpm.

 

[marlowmk2]

i had that same probelm in my 2000 focus w/ 2 pioneer 10" and a 800W amp, slapped on a cap and they work great, makes em hit harder too

 

[Dave A.]

Have you upgraded your alternator to accomodate the subs?

 

[Dave A.]

800 watts! Man, nothing like putting the stage right inside your car.

 

[MK2Racer]

Im running a Planet Auio 400x2 amp and 2 planet audio comp 12's, no cap and stock alternator. 4ga with one 80A fuse from battery to amp, 8ga ground wire. The voltmeter reads 14 volts when running, but the led next to it is always on. I think I posted about that earlier. Yeah, Im guessing it is dying, alt or something. Ill have ti check it out. Thanks!

 

[Dave A.]

That's too much load for the stock alternator. You really need to upgrade to a higher output alt..

 

[Henge]

It will be fine for the stock alt. Just put a capacitior in, it will help any power issues you have. You don't need any fancy capacitor or anything huge...just prolly a small little 1.0 cap. 800w is really not all that much :? Well it sounds small to what I'm used to I supose. 8) At nite try looking at your headlights while driving and turn your system up a bit... if your headlights dim when the bass hits then it is definatly a power issue. I suggest getting a cap. 8)

 

[MK2Racer]

They dim

 

[Dave A.]

Do your headlights dim each time the subs hit? Do you have one of those dinky little batteries instead of the regular size case style? :roll:

 

[MK2Racer]

I have a normal size battery, but it is old as hell. Ive had it through 4 cars and about 4 years. Actually, the lights dim only very slightly when the subs hit, but they flicker when I hit the brakes or turn signals. Also, I just got new foglight bulbs, 100w versus the old 55w ones and when my neons are on, then I turn the foglights on, they get dimmer.

 

[Dave A.]

Hmmm! Well, since the stock alternator is only rated at 60 amps max. output, my guess would be that if you were to connect an ammeter in series with the negative battery terminal and cable, run the engine at fast idle, and turn on all of your accessories and crank up your stereo, the ammeter would probably go into the negative, indicating that you're overtaxing your alternator and battery. A 1 farad monster cap would help with your peak current draw, but you still aren't eliminating the source of the problem. Lets say your peak current draw at the battery measures in at 50 amps. You would need a 100 amp alternator and a good high capacity battery to safely place that much load on the charging system. It's a good idea to keep the load on the alternator at about one half of it's max. DC current output rating or less to avoid overheating the alternator and drawing excessive current from the battery.
HTH!!

 

[MK2Racer]

Where would I go about getting a 100 amp alt. for a mk2?

 

[Dave A.]

Your 82 has the old style ND alternator ( provided that your alternator hasn't already been upgraded to the later style) so you could go with either a 80 amp MKIII alternator or a 100 amp MKIV alternator. Unfortunately, the swap isn't a direct bolt-in replacement on your 82. You would need to upgrade your drive belts and pulleys with those from a later model 84 and up MKII and change the engine wiring harness connector for the alternator and also do the charge light relay mod. that is specific to the 82 & 83 model year. I know this all sounds like a real PITB, but it's really not all that difficult if you can find all of the parts for a reasonable price.
27060-42030 is the part# for the 80 amp alternator.
27060-46120 is the part# for the 100 amp alternator.

 

[supra_toy]

One thing I notice is that you said you are running 8 ga ground wire and 4 ga power wire. The power and ground wire should be of the same size. So try upgrading your ground wire also try upgrading your under hood ground wire to a 4 ga from the negative terminal to the car frame. I did this and noticed a improvement... the problem your having could be just this.
I run (did in my last supra going to run in my new supra) a 700 watt Hifonics 5 channel amp. I did tax the electrical system a bit. I found that adding a good quality (PG) 1F cap took care of the light-dimming problem.
If your bat is 4 years old and its been through 4 cars it's time for a new one. If your want to spend the cash you could go with an optima red top or other deep cycle bat. I got by with a regular bat. I plan on upgrading to either the MKIII or MKIV alt soon myself just to make sure I have enough juice for all my planed electrical needs.
If your have any questions let me know I've done quite a bit of car stereo stuff.

 

[MK2Racer]

What precisely is the charge light relay mod?

 

[Dave A.]

The 82 & 83 MKII's have a relay incorporated into the charge light circuit that is designed to work only with the older style alternator voltage regulator. You have to remove the charge light relay by pulling it from the relay socket that's in the fuseblock located inside the drivers side kick panel and then jumper two of the four relay socket terminals with a 1N4001 rectifier diode. This is a very simple and cheap mod. that will convert your older 82 or 83 charge light circuit to 84 and up specs. and allow you to run nearly any later style ND alternator. I think Leslie may have the mod. diagram posted somewhere, but I'm not sure where? :?: Les,??