crcuevas

Hi all,

I have a LS400 1994 with about 230k miles. She was running fine for a while then suddenly i started getting the "lights dimming issue" and "radio dying" when I apply the brakes. I had the battery checked at a toyota dealer where I bought the battery and it was ok no problems.

I had the alternator checked at autozone where i bought it (lifetime warranty) they said it checked fine also. They told me that it be a bad ground or short somewhere. I check the voltage with digital multimeter and it does show that the voltage is slowly dying down. It starts at 14.2v and then in about 5 min its 13.4v and if I apply the bakes it goes down real fast to around 12v or lower and jumps back up to 13.4v and dying all the way down to 11.4v

But this is the second alternator in 2 years from autozone. I checked the wires in the trunk (driver side). No broken wires. My only choice is to take back to the dealer and do a diagnostic check for $100.

Am I missing something. I really do believe its the alternator again but can't prove it.

Chuck

rogzballz

iTrader: (9)

Sounds like a rusty ground somewhere, check the Ecu and fuse box areas...

Li Ls4

iTrader: (12)

try a new set of battery terminals. i had similar issue like that when i had my Ls and for me it turned out to be ****ty terminals surprisingly

RA40

iTrader: (6)

Yes, check the battery terminals for good contact. Alternators that have failed for me go out unexpectedly. You'll get the three warning lights on the dash indicating alternator failure usually.

This thread:
https://www.clublexus.com/forums/ls4...or-killer.html

Kansas

Sounds very famillar from my 13 1/2 years with a 1990 LS400. Is the power steering pump leaking fluid on to the alternator?

LScowboyLS

the Lexus dealership really isn't going to give you any more information for $100 than you can get yourself for free with a 2 inch piece of wire right here!

the only other thing they do is put a multimeter across the battery with both car off and car on and note the voltage. - Walmart has good digital multimeters for $20 - you are looking for at least 12.5V with car off and 13.6V with car on at idle. With a brand new battery installed, these two voltages will help you narrow it down to battery or alternator or connections.

I know what that $100 buys, I used to be one of their senior technicians.

PS - like Kansas said, if you are going through alternators, it is almost always because you are leaking PS fluid on to them.

crcuevas

Thanks everyone. I have no codes and I've cleaned all the battery terminals and ground wire and still the same. I even replaced the connector on the alternator. Where can you fine replacements for + battery terminal that fit our ls400? I know I can but the ground wire at any local auto place but the positive one? It has more connections.

Also, how do you remove the fuselink (fuse) for the alternator? It doesn't look burned but does have some green showing on it.

LScowboyLS

the + connection is available at any Toyota dealership, it fits about a bazillion Toyota models!

pretty cheap if ordered online p/n 90982-05037 about $14

and underneath that bolt that whole + terminal is often full of hidden corrosion!

crcuevas

Well I disconnected the negative side of the battery while the car was on and it took about 10min before the car died. I also had load on the alternator (lights, ac and pushed the brake pedal). Does that indicate a alternator problem or ?

LScowboyLS

disconnecting the battery while your LS400 is running is good way to mess up your ECU and other delicate system electronics - please don't do that

a pretty good on-vehicle alternator test is to just measure the voltage across the battery terminals at idle both loaded and unloaded, you can also do the same test both ways at 2500 rpm - at no time during these tests should measured voltage fall below 13.5V assuming you are starting with a relatively new and fully charged battery

j2b4o

When my alt went out it was strange. The car would start and drive fine but after a couple of stops it would struggle to find the power to start. Than a few days later it started real real slow and the radio cut out when I was lowering the window. I let te car sit a while and got my tools together and checked out the car. At this point the battery was a little low but not bad and when it started it had good voltage from the alt. however a day or so later it left me stranded completely dead battery. So I charged and tested the battery and it was fine. Next I started the car again and checked voltage for the alt. this time was slightly lower than the first time but still above 13.5v. I let the car idle in the driveway and warm up and checked again and now the voltage was something like 8.79v. Obviously the alt was toast. Got it tested after I pulled it out and every part failed the test. Ordered a new Denso OEM from rock auto and haven't had any problems.

If it ends up being the alt just be careful maneuvering the old one out and the new one in. It is a nearly impossible squeeze. I'm sure you could remove some stuff to make it easier but all I did was remove the brackets holding the power steering/trans lines around the oil pan.

crcuevas

Well I had my car checked out by indy and he could not find anything wrong. I don't beleive him because my lights still dim when I press on the brakes. I'm really stumped here

So again, is there anyway to test he alternator? I don't trust Autozone (where I bought it this is the second alt I replaced). The voltage drops from 14.5v to below 12v when I apply load for more then 15 min.

YAK00Z

If your alternator is gone, all the dash lights will still be on when the car is running, such as oil, radiator, engine etc. You do have a charging issue but if all dash lights arnt on, it hasn't kicked it yet. I've replaced two standard 100amp ones in my car to a 200amp high output to cut the problem.

KeyKeeper

Mine shows 13.2v running. I turned on the lights, AC, wipers, headlamps, and radio and let it sit for a few minutes. Ended up with maybe 9v at the batt. A little throttle and I'd get roughly 10.5v. I had all kinds of VSC/ABS lights coming on. Windows not rolling up right ect....stereo would cut out...I replaced the alternator and all is back to normal. If its a bad ground then it wont produce any more voltage when throttled than it does at idle. Resistance is resistance... regardless of the throttle butterfly position. However a weak alternator will put out more voltage when the armature is spun faster e.g. revved up.

LScowboyLS

Again, put a multimeter across the battery terminals at idle will tell you a lot, should be 13.6V or more

did you get a new positive terminal and a new battery so we are starting from a known good power source?