Sc0pe

iTrader: (1)

So not to grossly oversimplify things, but the flag terminal and A/C compressor grounding points are strictly grounds for the battery, correct? Nothing else is grounding to them besides the battery's negative terminal?

The reason I ask is since I'm getting ready to do the big 4 (more commonly known as big 3) wiring job (battery + to alt +, battery - to chassis, alt - to engine ground, engine ground to chassis). I had replaced my OEM terminal with a generic terminal (negative terminal stud broke, and lost its clamping force over time - was out of town so I just used it as a quick fix) awhile back. The issue I'm having now is the generic negative terminal also doesn't have enough clamping force to grab onto my side-post (OEM negative cable was too short after being cut, so relocated the battery terminal post with a side-post adapter), and just sort of freely wiggles around on the connection. It still maintains contact, but it's not what I consider to be a solid connection.

I was wondering if I could just disconnect/remove the negative terminal and cable altogether and rely on the new ground wire I'm running to a bolt on the strut tower.

YODAONE

To the strut tower you say?

Anyone care to field this one?

Sc0pe

iTrader: (1)

Yeah, a lot of people I've talked to in car audio circles, and in general, suggested the strut tower since it's usually closest/easiest (shorter runs = less resistance, and so on) to get to from the battery in the engine compartment. It's also a major structural component on a unibody car which makes using it as a grounding point pretty close to a "frame ground."

YODAONE

With LS400 the negative cable connects mid-point with flag lug aside the lower strut tower structure, and terminates at engine via the A.C. Compressor.

The starter is in engine block so a direct negative battery connection to engine block is important.

So bypassing the engiine by directly grounding to the top.of the strut tower is not recommended.

This project uses premium marine fine strand tin-plated 4 gauge, over stock unplated coppee thick strand 6 gauge (if.OEM had used 4 gauge, the marine 4 gauge cable is superior), significantly improved lugs and battery clamp to reduce resistance and increase current carrying capacity...so not necessary to reroute your negative ground.

If runnimg high amperage amplifiers then perhaps a direct negative cable to the unit would offer advantages

The A.C. Compressor clutches on our LS400's seem to last a long time...possibly because they have direct connection to negative battery terminal

Sc0pe

iTrader: (1)

Ah okay, I didn't think of it that way. Looks like I'll probably just end up ordering this replacement cable and doing the strut tower bolt ground as more of a complementary addon. What are the odds you know how much slack there is with this cable? I'm using a standard Group 24 battery, instead of Group 24F, so my terminals sit an inch or so further up (closer to the middle of the battery) than stock.

YODAONE

Installed the new cable assembly today.

Everything fit perfectly...better than new.

The new negative battery terminal clamping bolt required shortening to accommodate the plastic OEM negative clamp cover.

A Sharpie and Dremel tool remedied this. The original negative battery cable assembly in retirement.
QuickCable's negative battery clamp clamping bolt is too long, to allow OEM plastic cover to fit, so cutting is required.

Negative battery terminal clamp cover fits like a glove

YODAONE

The weather is turning cold in Chicago, so while running heater blower fan at medium-high, turned on rear defogger (big current draw...idle drops), front defogger (AC compressor and clutch), headlights, windshield wipers, radio (with volume down but CD player on)

The heater blower did not dip in RPM as before...(barely..)so an improvement.

This project began to resolve blower motor RPM drop: apparent wiring capacity bottleneck(s) or charging system deficiency...(my opinion)

The positive cables will receive attention as well.

Stay tuned....

Also, if anyone replacing their alternator then check out my post on using 2001-2003 LS430 130A (2004-2006 uses incompatible 4 wire plug) alternator. (more efficient wire and winding configuration)..literally plug and play for 1995-2000 LS400... 1990-1994 LS400? (if equivalent housing and mounting holes) utilizes different harness connector, but purchase contacts and correct connector shell from Lexus. (Contact Lexus to determine if same harness contact pins and use technician to verify correct contact wire orientation)

Sc0pe

iTrader: (1)

Do you know when the revised negative cable will be available to order from QuickCable?

YODAONE

P.M. me for availability. Thanks.

smamas

Is this cable available yet or can you buys the parts and assemble yourself?

YODAONE

Am in process of assembling parts to modify the Alternator postive terminal to battery cable to 4 gauge...

While researching vendors for the correct replacement postive alternator lug, came across a post regarding a Toyota 4-runner:

https://www.toyota-4runner.org/3rd-g...n-t4r-how.html

One thing that makes sense is to extend the main negative ground cable from the compressor stay to the alternator.

As it is now, LS400 alternators ground through the engine block via steel zinc-plated bolts and then to the negative battery cable.

In the article the author fastens an unplated copper lug directly to the Aluminum alternator housing which ignores dissimilar metal corrosion...

Also, QuickCable offers superior lugs and cabling over auto parts store stuff.

Will begin a separate post on upgrading alternator positive cable to 4 gauge tin-plated fine-strand marine grade cable.

Here is image of part I am seeking for that project:

Anyone know P.N. or where to acquire mating alternator positive terminal lug for Denso alternators used in LS400?

Les916

hello fellow lexus buddies. first time posting but ive given trying to research and ive read alot of your guys posts. i know im ask the right ppl cause you guys are very knowledgable when it comes to these stuff. i have a 2001 lexus gs 300, by any chance does anybody know what is that other wire that is coming from the ignition with the trigger wire? that connects to the starter. i hope that makes sense. i noticed a grey plastic square attached to the engine blocknext to starter. is that where that wire is supposed to be connected? i hope i described it good enough so it can be solved. i have a no crank no start and believe that is the culprit. if you can include images, it would be appreciated. thanks guys.

xty1ch

I'm new to this whole thing and I have a 1998 UCF20 LS400 and am almost finished getting the car running. I currently just need an OEM battery tray which I know are discontinued and can't source any locally (have tried junkyards, recycling areas for parts, etc), but the last thing is this one negative battery connection coming out of the harness from starter to battery terminal. I know you can just ground these anywhere to a ground however the access areas near it are little and far. I'm being told to try and find something called a "sheet metal clip" which is similarly used under the airbox on passenger front.


Any help or criticism will be appreciated haha thank you!

ShelbyGT

YODAONE!!! I have a 91 LS400.. I had a terrible negative cable and I foolishly change the cable but I didn't realize that you couldn't just put 2 cables together and ground them.. My car will not crank. All the lights, bells, whistles, radio come on but it will not crank.. The only thing it could be from the research I have done on this forum, ( and I have read hundreds of posts) is that I am not getting a proper ground. (It has done this once before, and it was not grounded properly). Please tell me how to go about getting that special cable! I MISS DRIVING MY CAR!!!!

deanshark

I could be wrong but this sounds like you might have set the alarm. I had the same symptoms on my old 93 a couple times when the alarm got set. Try unlocking the passenger front door with the key twice. That resets the alarm. Just a thought.