DumpBox

Ive been trying to find anything on here related to the issues im seeing and have had no luck.

I was seeing all of my dash lights come on intermittently and when they would be on the battery wasnt being charged so I replaced my alternator back in october of '13 and had little to no issues until a few weeks ago, when my alternator connections physically lit on fire. My PS isnt leaking and there was no liquid or residue on the alternator itself. So I repaired the harness/wiring and installed another alternator. It was fine until friday night when all my dash lights came back on and my battery isnt getting charged again.

I am NOT running an alternator heat shield or an under car shield. Both werent there when I bought the car.

Does Anyone have any advice or have you seen anything like this before? I heard about someone running a new wire from your alternator somewhere? I need help, it is such a great running car and super reliable. Just has the gremlin and I cant figure it out.

Any help Is appreciated.

LScowboyLS

what kind of aftermarket non-stock crap is currently installed on this car or was installed previously, i.e. bigger stereo/subs/amp, or HID headlights, etc.

Is the car lowered, slammed, etc. now or in the past? (the main cause of shorts in LS400)

these types of issues will fall into the above two categories, a stock, never-modified LS400 doesn't have any weird electrical problems/shorts/gremlins unless someone has messed with the wiring.

so figure out what areas have been messed with previously, and you will quickly locate the issue!

sha4000

iTrader: (1)

That's kind of weird. What year is your car? Like LScowboyLS asked, have you or anyone else hacked up the wiring to install any aftermarket stuff?

DumpBox

Its a 1991. It Does have an aftermarket head unit. No subs and never been slammed.

Think it could be related to the stereo? Where should I look first?

dengman

what alternator was installed? If its has too little or too much voltage it will stop charging the system. Possibly the alternators regulator is bad? Just because the car is entirely stock doesnt me an it cannot have wiring issues. If there was a rats nest in the car at one point in its life I'd be worried.

DumpBox

Well I just put the alternator in last weekend. It was a remanned delco, I had it tested before I installed it and it passed so I assumed it was good. Like I said it has an aftermarket stereo head unitx where woukd the wiring issues generally be on a stereo? It worked fine until friday night, then every warning light on the dash came on and now its not charging the battery anymore. Where should I look first?

dengman

I would test the charging system and see how much voltage its putting out. If its putting out too much voltage it would trigger the dash light but still be charging, I believe.

IE my 99 LS had a bad alternator it was only geting 8volts at idle and dash light was on but when I drove it and got the rpms up to 2.5k it got the proper voltage and the dash light turned off.

DumpBox

How do you test tge charging system? Just meter leads across the battery? My lights come all at once, when they are off everything is good, when they are on my battery is being drained. The first time I replaced itx it took months for it to happen again, this time, just one week. Im scared to put anpther alt in if its gonna happen again in a week. Any help is appreciated.

LScowboyLS

also, please try a brand new battery - a bad battery can kill an alternator, and a bad alternator can kill batteries!

aomdedude1

LS, could you expand on this? How does lowering lead to shorts? I'm just curious! I've been thinking hard about BC coil overs...

I don't mean to go off topic!

LScowboyLS

it seems that nearly every electrical problem on a lowered Lexus is eventually resolved once it is discovered that the wiring harness has been cut into by the lowered body or a wheel or a suspension part, all due to the lowering being done by companies or owners who are not conscientious about the safety of the wiring harness and how it might be exposed to danger on bumps, turns, etc.

the only four electrical problems you will ever see on a bone-stock LS400:

● alternator failure due to being doused with power steering fluid (not the super-reliable Nippon Denso alternator's fault at all)

● driver's side trunk hinge wiring break in pre-95 models

● cigarette lighter fuse link

● positive battery terminal end corrosion under bolt that is a couple inches from battery post where terminal attaches to positive cable

Shmee

iTrader: (3)

Sorry but this is entirely false.
Lowering a car does not cause the body to cut into wiring harnesses, ever. In vary rare circumstances people have cut into a harness with a wheel/tire, but that is with a fairly specific setup.... Not just because they lowered the car.

There are more than just this.

Shmee

iTrader: (3)

One thing to check is the alternator/power connection to the fuse panel under the hood.
the bolt above the Yellow fuse on the right hands side of this pic:


I am not at all familiar with then 90-94 cars but when I was looking for my 96, I noticed more than a few cars had corrosion, or arcing around the cable/nut due to a loose bolt. if it is loose, disconnect the batter and remove the nut from the stud, clean the contact point of the terminal and the cable with some emery cloth/sand paper, put the cable back on with a thick washer under the nut and tighten it back down.

An alternator catching fire is a fairly serious issue and could be cause by a number of things...

LScowboyLS

the corrosion under the positive battery cable to terminal nut is not due to being loose, it is due to a scientific phenomenon known as galvanic corrosion - Yamae and I have both given technical explanations on this in the past.

python

iTrader: (4)

also known as electrolysis,is based on two dis-similar metals in contact..and can be formed with water as well