Sc0pe

iTrader: (1)

I would like to preface this by saying that I have 1999 LS400 with a high amperage alternator, and my charging system is functioning completely fine.

I mainly want to know what causes the Battery Light to stay on constantly, and what the Headlight Leveling System looks for before displaying an error message on the dashboard, because it's functioning with no issues, and from my understanding it's usually more of a warning for the electrical system.

I want to clarify that I am NOT looking for what the Battery Light and Headlight Leveling System error messages are symptoms of, but rather what conditions have to be met/not met for those error lights to display.

As far as my charging system goes, I have a 320A Mechman alternator which charges fine at idle until I shift into drive, at which point the RPMs drop low enough that it doesn't charge., When I give it the slightest amount of acceleration it starts charging again. In any other gear, it charges completely fine at 14.2V. All main wires have been upgraded to 1/0 gauge, and the grounds are bare metal, so I know it isn't an issue of resistance.

Yamae

The original Denso alternator's signal line "L" is designed to interface with the ECU. Did you confirm that your Mechman alternator has the same interface with Denso's?

Many aftermarket alternator's "L" lines are designed to drive a bulb and those can't interface with the ECU properly.

YODAONE

Had discussions with Mechman, reviewed specs and based on at idle performance determined not to recommend it for LS400....

The 2001 -2003 LS430 130A alternator is a bolt in replacement and improves power under the curve at idle over the stock 100A OEM alternator.

See:

https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/807894-1998-2000-ls400-alternator-upgrade.html

Sc0pe

iTrader: (1)

I have not confirmed this with Mechman yet, but I'll check with them now and see. Do you know what kind of signal the ECU looks for from that wire, in case I could modify the signal coming from the Mechman alternator?

Yeah, when I spoke to Mechman, they said the 1UZ idles so low that the alternator doesn't spin fast enough to charge. At the time I ordered the Mechman alternator they didn't know about this issue, but I picked it over alternatives because of its 320A output rating. If I wasn't running as many accessories, then the LS430 alternator would make for a good OEM+ upgrade.

timmy0tool

iTrader: (7)

can't really contribute here but I'm glad to see you still around and kicking man!
hydraulics I'm sure draw a ton of current, and with the sensitive ECU these cars have I'm not surprised it doesn't like this heavy of a modification to its charging system.

do you have additional batteries too?

Sc0pe

iTrader: (1)

haha, I've been around. I haven't finished installing the hydraulics yet, but that system will be running off of a separate bank of batteries (sounds like a lot, but it's just two batteries wired in series for 24V) that will be charged by a StreetCharger unit (basically steps up the voltage from the car's charging system to charge the 24V bank off the alternator). Technically I could run it off of the factory 12V charging system, but I read that hydraulic pumps pulls a lot of power when in use, so I figured isolating it to a separate battery bank would put less of a load on the car's electrical system.

I opted for the higher output alternator since I have plans for a big sound system later, but being able to support the charging system for the hydraulics is an added bonus.

Yamae

It is a good idea to modify the signal. The ECU's specification of the interface voltage of "L" is specified as follows.

When charging: 1.5V ± 1.5V
When not charging: 11.5V ± 2.5V

I'd add a home blew circuit to perform these 2. The problem is that the specification does not say any about the impedance or the current. You probably need to cut and try some.
Good luck.

Sc0pe

iTrader: (1)