Headlights Dimming After New Amp Install

kr8zeivan · Post by **kr8zeivan** » 25 Mar 2013, 20:45

Hello everyone. I am a new Volvo owner and new to the forum. Just picked up a pristine 1999 S80 2.9 non turbo. I love it. Great car. I am looking for some guidance. Seems like this is the best place to start. I just installed a JL Audio J2 500.1 running a Rockford Fosgate HE2 DVC 10" in a SubZero Bandpass enclosure. Hits really hard and sounds awesome. Problem is my headlights dim whenever the bass or drum notes hit. I am thinking of doing the Big 3 Upgrade, and /or installing a higher output alternator. Has anyone done this before on a 1999 S80? Which is better? I am confused because the battery is in the trunk and not sure how the Big 3 can be done on this car. BTW I kept everything else stock. Stock HU-611 premium amplified set up. I tapped into the rear speakers and used an in line converter for the RCA hook ups to the amp. Any help would be appreciated.

Post by **precopster** » 26 Mar 2013, 04:47

Start with wiring and work your way back to the alternator (usually a 120A)

You may already have a 160A alternator so check the alternator when dark with a torch light and you should be able to see the markings.

How much current draw (or watts in power usage), and I'm not asking about watts of sound to the speakers but power usage that the sound system draws from the electrical system. It should be stated in the manual.

kr8zeivan · Post by **kr8zeivan** » 26 Mar 2013, 05:54

Thank you for responding. I used 4 AWG OFC cable for my amp install and have it fused right next to battery.I went through the manual and found nothing on watts usage, but I tuned it with a voltmeter to about 30v at 2ohms pushing around 500w to the sub. The local stereo guys suggested I beef up the car negative ground and battery positive to 0 AWG OFC wire and also the alternator positive and positive to chassis cables. I am just a little unsure how to since the battery is in the trunk and I know these cars can be finiky when it comes to electrical stuff.

Post by **precopster** » 26 Mar 2013, 06:07

AND it's an S80 where electrical cleanliness is essential due to the amount of on-board computers within the vehicle. I hope you really don't mean positive to chassis cable (that would kill your car's electrical system in no time

)

Just behind the engine bay fusebox you'll see the positive terminal junction with a flap to access it. This is where your positives junction from the battery to the alternator (large red cables)

Not the easiest car to upgrade. Always reconnect power while ignition is in Pos II for best results (this helps the modules start up)

kr8zeivan · Post by **kr8zeivan** » 26 Mar 2013, 06:46

I meant engine ground to chassis, alternator positive to battery positive (this is where I get confused because it really doesn't run to battery in this car), and battery negative to chassis. Oh so I always reconnect with key in ignition to position II. I thought it had to be completely off. Thanks for the heads up. So then do I upgrade the cables from the terminal junction to 0AWG? Then the positive from the battery to its terminal point? Did that make sense?

Post by **precopster** » 26 Mar 2013, 12:01

Just run a replacement B+ cable to the beforementioned junction area in the engine bay from the alternator as well as an upgraded engine earth and battery to chassis ground in the rear battery compartment and see if this improves things.

If there's only marginal improvement you may need to investigate replacing the positive lead from the battery to the engine junction area (a pretty complex task)

Perhaps the latter improvements and a deep cycle battery will be enough in your case without replacing the long positive. Not many of us here have upgraded the factory units in our P2 series cars because:

a) Some of us are too old for all that trouble, me included
b) The factory head unit and speakers already make our heads spin with great volume and reasonable bass.
c) If it's working just fine most of us would rather leave things be
d) We have adequate volume for drowning our wives' voices while washing the car

kr8zeivan · Post by **kr8zeivan** » 26 Mar 2013, 20:24

Awesome. Thank you for the information. I will try that and post my results. Your explanations are clear and make sense. I will do this in the next day or so.

mjbaker23 · Post by **mjbaker23** » 24 Mar 2015, 16:55

Hi. This is the first post I've replied to as I've only had a Volvo for a week. It's been a couple of years since your question and you've probably got it sorted now, but I thought I'd offer some advice. I had an active 1600w 12" Vibe sub in my old Peugeot and the headlights dimmed with the heavy bass and it ruined the battery and alternator after 2 months. I changed the battery and alternator and bought a 6 farad capacitor and the headlights stopped dimming after that was installed and the bass sounded much louder and clearer. There are lots of good and bad comments about caps, but I thought mine was a good solution to the dimming headlights.