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Hey guys, new to the website and GS community. Got my 98 Gs300 back in October and finished rebuilding it around mid January, only problem I'm having now seems to be alternator not charging battery.
-Car reads at 11.6 running, no drain when off
- I have changed batteries
-Tried 1 used alternator, 1 reman, 1 claiming 200amp output
- no battery light ever and rpm gauge won't budge, connecting these 2 problems together I tried changing the bulb and swapped with a junkyard cluster with no change other than mileage
- my brother said he checked all grounds, wire continuity, fuses
- took ECU apart and had some brown oil maybe motor oil, cleaned it and put it back in
-car did sit for 4 months before I bought it, maybe mouse chewed something up under dash?
- I also replaced the 3 pin alternator plug with no change, replaced cause the other one was in terrible shape
I would appreciate any and all help, thanks.
Last edited by AveryWhite; Feb 24, 2023 at 09:35 PM.
Reason: Typos
WOW! This sounds like a real interesting problem. So let's start by stating you have two problems.
1. The alternator doesn't charge the battery.
2. No tach on the cluster.
True or false?
If true, let's ignore the cluster for now and just deal with the alternator not charging.
Here is the wiring diagram for your car. It is from the year 2000 Electrical Wiring Diagram. Do you know how to read diagrams?
There's not much going on here. You did not mention a "Charge" lamp on the cluster.
You also didn't mention any DTC's (digital trouble codes) from a scan.
So. Does the car start? Does the A/C run? Does the Multidisplay light up? What else doesn't work? Lights? Horn? Anything that you can turn on and off. Get back to us when you get a minute to check things out.
WOW! This sounds like a real interesting problem. So let's start by stating you have two problems.
1. The alternator doesn't charge the battery.
2. No tach on the cluster.
True or false?
If true, let's ignore the cluster for now and just deal with the alternator not charging.
Here is the wiring diagram for your car. It is from the year 2000 Electrical Wiring Diagram. Do you know how to read diagrams?
There's not much going on here. You did not mention a "Charge" lamp on the cluster.
You also didn't mention any DTC's (digital trouble codes) from a scan.
So. Does the car start? Does the A/C run? Does the Multidisplay light up? What else doesn't work? Lights? Horn? Anything that you can turn on and off. Get back to us when you get a minute to check things out.
Paul
when my brother did a scan only code was for a neutral safety switch, I thought I mentioned the battery lamp not working at all? Yes the car starts up, why the sarcastic attitude or am I misunderstanding?
LOL. You are misunderstanding. No diss intended. It's almost 12:30 AM here in CA. And I do find it an interesting problem.
The fact the car runs eliminates the ECM. The Combination meter getting power eliminated that. There is a 5 amp ALT-S fuse that you should check. If the A/C works and the tilt steering works you can eliminate that. With that out of the way you are looking at doing continuity checks on the wiring harness.
LOL. You are misunderstanding. No diss intended. It's almost 12:30 AM here in CA. And I do find it an interesting problem.
The fact the car runs eliminates the ECM. The Combination meter getting power eliminated that. There is a 5 amp ALT-S fuse that you should check. If the A/C works and the tilt steering works you can eliminate that. With that out of the way you are looking at doing continuity checks on the wiring harness.
Paul
Thanks, you're definitely narrowing it down for me. Yeah the tilted steering works and the a/c, I have a buddy sending me his rebuilt alternator, hopefully the rest were actually bad. I don't think I'm that lucky though lol. And I have the wiring diagram on my phone but as of now I still don't understand how it's used correctly haha I'm definitely new to this, my brother was supposed to finish everything but moved on to his personal project. I forgot to mention my transmission floor shifter is stuck, though I suppose it could be related to the charging system problem. I'll try to upload videos and photos tomorrow if it helps, tried earlier but it wouldn't cause file was mp4
Absolutely no problem. I'm just a 63 year old electronic tech that knows what a pain these types of problems can be. But yours was one that I almost never hear of.
Theres still some other things. The fuse block, electrical plugs and yes Rats. Newer insulation is SOY base if you can believe that and rats love it. Considering that she sat for four months, pretty much anything is on the table. But just making sure you have no open wires is the first thing. Hand over hand the harnesses if you can just to see if anything is chewed or burned. The electrical wiring manual is pretty cheap on ebay. Usually around $40. It pays for itself. I couldn't function without them. I have a 2003 GS430, a 2002 SC430 too along with two more cars. Spent last weekend changing knock sensors and starter on my SC because of a rat. Before. After.
You can always pay someone else. But the sense of pride and money saved does it for me.
Absolutely no problem. I'm just a 63 year old electronic tech that knows what a pain these types of problems can be. But yours was one that I almost never hear of.
Theres still some other things. The fuse block, electrical plugs and yes Rats. Newer insulation is SOY base if you can believe that and rats love it. Considering that she sat for four months, pretty much anything is on the table. But just making sure you have no open wires is the first thing. Hand over hand the harnesses if you can just to see if anything is chewed or burned. The electrical wiring manual is pretty cheap on ebay. Usually around $40. It pays for itself. I couldn't function without them. I have a 2003 GS430, a 2002 SC430 too along with two more cars. Spent last weekend changing knock sensors and starter on my SC because of a rat. Before. After.
You can always pay someone else. But the sense of pride and money saved does it for me.
Paul
Yeah I might end up getting a wiring manual, I know in the cabin air filter area I seen a mouse/rats nest. Only one I seen in engine bay was under the master cylinder, I'll definitely get some pics tomorrow or later today of interest points. I thought about hiring a mobile mechanic but everyone in my area seems too lazy or not qualified enough for my issues. Was hoping my rpm, charging issue, shift lock, no battery light were connected to the same issue so narrowing down the issue wouldn't be as difficult lol
Absolutely no problem. I'm just a 63 year old electronic tech that knows what a pain these types of problems can be. But yours was one that I almost never hear of.
Theres still some other things. The fuse block, electrical plugs and yes Rats. Newer insulation is SOY base if you can believe that and rats love it. Considering that she sat for four months, pretty much anything is on the table. But just making sure you have no open wires is the first thing. Hand over hand the harnesses if you can just to see if anything is chewed or burned. The electrical wiring manual is pretty cheap on ebay. Usually around $40. It pays for itself. I couldn't function without them. I have a 2003 GS430, a 2002 SC430 too along with two more cars. Spent last weekend changing knock sensors and starter on my SC because of a rat. Before. After.
You can always pay someone else. But the sense of pride and money saved does it for me.
Paul
Here's photos I took of some interest points, might try to take dash out tomorrow if anything charging related goes through there Mouse/rats nest in cabin air filter, any important wires back here? Wiring above cabin air filter Cluster first activated Engine off after other lights go away Radio area, last owner did wiring for subs I don't know where you attach this to lol Mouse nest under master cylinder, probably nothing important down there? Ground terminal replaced, positive I haven't (don't think there's too much rust) I don't know what this goes to but I think it's part of the aftermarket headlight bulbs 1/2 2/2 Before this alternator plug was sketchy at best, I rewired a oem one (I know I should heatshrink it and tape it up) Tried to get a better photo but this above the timing belt/camshaft gears. Only seen this one wire open but not frayed or rusted/burnt( I think it's a power wire but not 100% if this could cause 2v loss)
Yea. When I bought the GS430 I had to go through and rip out a bunch of aftermarket wiring. I already see splices from a previous repair. The open wire, what color is it? I can probably find it in the schematics. Really busy right now though and it looks like you need some serious help. Wish I could be there personally. All I can say is buy the Lexus Electrical Wiring Diagram book because I'm sure your going to need it anyway.
And I have no idea what the two red lamps mounted in the plastic area of the cluster. My guess would be an aftermarket radar detector. RIP it all out and get yourself back to a good starting point would be my recommendation. Gotta go.
Removing the dash is an absolute last resort. On utube there is a channel called "The Car Care Nut". Ex toyota master mechanic. He pulled a dash a few months back because of an A/C issue that you should take a look at. Good videos with a couple of decades of knowledge behind them.
The open wire is red with black lines/strip. I'll order that book asap. I don't need to drop the steering column to get the dash apart do I?
It depends on how deep into the dash you need to get. You can pull the instrument cluster without dropping the steering, but if you want to go further dropping the dash is a BIG job. You pretty much have to dismantle everything from the center console storage boxes forward to get it off. There are several wiring harnesses that are clipped to the underside of the dash so you need to either cut the wire ties or fiddle with the screws holding the clips in place.
it took me most of a day to get it apart and a day and a half to get it all back together. Lexus builds the car with precision, and it must be put back together in the exact reverse order to the way it was disassembled. If you have to force anything, it means that you missed a step and you have to go back. It’s an interesting challenge.
Removing the dash is an absolute last resort. On utube there is a channel called "The Car Care Nut". Ex toyota master mechanic. He pulled a dash a few months back because of an A/C issue that you should take a look at. Good videos with a couple of decades of knowledge behind them.
Paul
Man he's such a nice guy and explains things very well, I also watch a bunch of others like Scotty Kilmer, Questionable garage, tavarish, and chrisfix. However I can't find anything similar to my issue unless search algorithm garbage.
A few things I thought about last night
- before swapping old battery I got 14v when charged but with drain, after cutting cord from sun on positive terminal could this be a cause of a 2v loss? Sorry for asking so much but I know nothing about subs, not into all that.
- when I turn on headlights one flickers, could this be a short? But still don't explain the 2v-3v loss
Help! Charging system issues
