bad dimming after new amp install

ASSISTANCE Electrical & Entertainment Systems
1

So I just installed a new JL 750/1 amp pushing a RE SE 12" and I have horrible dimming problems now. I can’t even really turn it up with my headlights on, it looks like I’m flashing people almost. Without my headlights on it doesn’t seem too bad, but who knows.

So what can I do so my car can handle the amp? I’m not sure if it’s a grounding problem somewhere because my headlights dim pretty bad without the amp anyway, like when I hit the brakes or sit at a idle. Or if the charging system just flat out isn’t able to handle the power. The alt. is good, I just replaced the brushes in it, and I have a relatively new optima redtop (biggest one they make). Would a cap do anything? I’ve heard mixed things about them so I have no idea. So if anyone knows where to start let me know.

It sucks to spend the money on some nice equipment for once only for it to be basically useless in my car. :down:

2

A few questions…

MM&Y of car?

What other mods, other then audio system, have you made to the car?

Is the JL Audio 750/1 the only off-board amp in the audio system?

What gauge is the power and ground cables for the amp?

How long is the amps ground lead and where and how is it grounded?

What type of fuse and fuse holder are you using on the amps power lead?

Have you “beefed up” the batt. to chassis ground?

You said, “I have a relatively new optima redtop (biggest one they make)” does that mean the batt. is relocated?

If so, to where and how is it wired and what gauge cable is used?

Have you had a proper load check done on the cars charging system?

If not, have one done, most alt./batt. shops will do this for free, it takes only a few minutes.

A cap can help, in your case there is some other problem because you had a dimming problem before amp was installed, this needs to be fixed first.

I would start by checking/re-doing all the main power and ground connections, the stock ones, this will of coarse depend on if the batt. is relocated or not and how it is wired.

Please answer all the above questions as best you can, pix will also help. 94

3

  1. Car is a 1990 Integra GS coupe with a 99’ B18B. But it still has the old non-obd alternator with new brushes.

  2. No real mods to car other than audio system (that would effect the power anyway). Car has alot of suspension work and a I/H/E but I don’t see what that would change.

  3. Yes the 750/1 is the only amp in the system. My whole set-up just consists of a deck, two 6.5" speakers up front, and the sub/amp in the trunk.

  4. I used 4 guage for the power and ground for the amp.

  5. The ground is maybe 3 feet long at the longest. The amp is mounted on the back seat and I have it grounded underneath the bottom of the back seat to the seatbelt bolts. The way I did it though I didnt actually run a bolt through the ring terminal into the chassis. What I did instead in scrap off all the paint under one of the seatbelt brackets that bolt the seatbelts down, and just used the bracket to sandwich the ring terminal down to the chassis. I figured that was better than using a self tapping screw or something. It’s secure as hell because you can torque the crap out of those big seatbelt bolts, and I made sure to remove all the paint. Should I change this ground?

  6. I’m using just a standard inline AGU fuse holder with some 60 amp AGU fuses. Think I got them from knukonceptz if that matters. I can pop them when turned up though and I’m using the reccomended 60 amp fuses for the amp.

  7. I havent upgraded any factory grounds what so ever.

  8. Battery is in it’s stock location still.

  9. I have not had a proper load check done by a shop or anything. I’m not sure what a proper load check consists of but I have checked it out with my multi meter and it seems to be reading about 14.8 when first turned on with a high idle and then bounces between 14.55-14.6 at idle once fully warmed. Seems okay to me. This is with basically nothing turned on though. No stereo, lights, fans or anything.

I was planning on doing the grounds under the hood once it warms up a little. No garage = not much work being done in the winter. What grounds should I upgrade exactly? And I can take pics tomorrow when it’s light out if you would like to see something in perticular.

4

The amp ground is good although longer then I would use.
Is it possible to shorten it?

Power and ground cable gauge is good.

I would replace the AGU fuse and holder, with an ANL, [wafer] fuse and holder, I recommend the post type, [nut and bolt] fuse holders, like this… http://www.scosche.com/products/sfID1/151/sfID2/160/productID/1765

I would also recommend, [if not already done] that the ring terminals are soldered to the power and ground cables.

I would “re-do” the main power and ground connections, starting with the grounds.

Remove the batt. for access to chassis ground, remove ground cable at both the chassis and engine, clean all contact surfaces and reconnect the ground cable and reinstall the batt., do the same with the main power connections…

Batt. to engine bay fuse box, alt. to engine bay fuse box, [both ends] and the main fuses in the engine bay fuse box, [the ones screwed down] same as the grounds, remove clean reconnect.

You must “beef up” the batt. to chassis ground, add a 4ga ground from batt. to chassis, shock tower studs work well for the chassis end.
Remember, you are running a 4ga power off the batt. but have only the stock, [6ga maybe] ground from the batt. to the chassis.

Once the above is done have a proper load check done, a meter will tell you very little about the charging system, 14.5V is OK, but what is the current, [amperage] 25A will not get you far.

I always get a little concerned when alt. voltage is over 14.5V, possible voltage regulator issue.
Because you had dimming problems before amp was installed you have either power or ground connection problems or a bad alt., that’s why you redo the connections before doing the load check.

If alt. needs to be replaced, replace it with a high output alt. and you will not need the cap.

If once the above work has been done and the alt. checks out, [load check] and if you still have some dimming issues, add a 1 farad cap. 94

5

Do the big 3 upgrade. If that doesnt work upgrade the alt.

http://ezinearticles.com/?The-Big-3-Car-Audio-Wiring-Upgrade&id=1411196