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Installed new belt, cables, and a 165 amp alternator, now the lights dim?

SyCo

NAXJA Forum User
Location
Spokane, WA
98 4.0L 135K. Two amps pushing about 860watts RMS.

Today I installed a 165 amp alternator I picked up off of eBay. Battery cables are Jeepers Creepers and a 2ga alternator -> PDC cable with a 200amp inline fuse. Also installed a brand new Dayco serpentine belt a week ago.

First impressions are that all the lights are brighter, interior and headlamps, and the music seems louder at my "regular" volume setting.

I've been having some electrical gremlins which include the lights dimming, the voltmeter gauge jumping all over the place, the XJ needing a jump start for no apparent reason. I was hoping that the new alternator would've fixed these problems, most of them seemed to disappear when I installed the new belt, including the lights dimming.

However now when driving and the music cranked all the lights intermittently dim. The problem is only while driving, no problems at idle with the music at the same volume. I have an Optima Red Top that's got a good 4-5 years on it. I think it's time for a new Optima, but are there any other problems it could potentially be? Tension on the belt is between 140-160lbs, I tripled checked. Thanks.
 
Was it a NEW alternator? If not, it might be junk. Even if it is, it might be defective. My last alternator, brand new, failed after about two months. Fortunately I had it repaired under warranty, it was just the regulator.

There's lots of alternator troubleshooting info out there, none of which is really specific to XJs.

What is specific to XJs is crappy grounding. Disassemble, clean, and reassemble all your electrical grounds, engine block, firewall, dipstick, etc. A small amount of noalox or similar will help prevent future corrosion. Sounds like something might be wiggling around and opening a ground connection. Or something might be shorting out. I can really only theorize that something is physically moving around while you're driving.

The more I think about it, the more I think you have a short somewhere. That would certainly explain needing a jumpstart.
 
Yeah it was a new alternator. I used noalox on all my connections as well. I'm going to recheck the tension on my belt today, and might go buy a new battery too.
 
One thing alot of people over look when putting in amps/subs etc. is a Capacitor before the amps. I would disconnect the amps and see if things change. Just sound to me that you over working the alt and battery.
 
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