Low voltage after new battery and new alternator?
#16
Lexus Champion
Don't blame the alternator until you are POSITIVE the battery is good. I jumped to conclusions a few years ago, blamed the alternator, took it out and had it tested at two places. It was fine. CRAP!! Turns out the cause of low voltage readings while running under load/no load was a flaky cell in the battery. Have THAT tested first.
#17
Driver
Thread Starter
This is what it reads at idle
This is what it reads in the trunk while running. I turned up the music and the voltage barely dropped. I still think it should be higher?
This is what it reads in the trunk while running. I turned up the music and the voltage barely dropped. I still think it should be higher?
#18
Lexus Champion
yes, should be higher, more like 13.8V or more, try these two simple fixes first, before buying a new alternator
● a new battery (not kidding)
● this $15 part from any Toyota dealership (the factory + terminal), p/n 90982-05037 (they get hidden corrosion in the inside, robbing power)
although from looking at your pic, your positive battery terminal is a ways from stock, are you using a + battery cable of at least the factory quality and gauge?
the LS400 alternator is kind of on the edge of what is required, just for the car, if it is stock, that is just 80 amps and doesn't really have any extra current for your big mystery extra wire
also, in your pic, where are you taking the measurement? - we can't see where the test leads go!
● a new battery (not kidding)
● this $15 part from any Toyota dealership (the factory + terminal), p/n 90982-05037 (they get hidden corrosion in the inside, robbing power)
although from looking at your pic, your positive battery terminal is a ways from stock, are you using a + battery cable of at least the factory quality and gauge?
the LS400 alternator is kind of on the edge of what is required, just for the car, if it is stock, that is just 80 amps and doesn't really have any extra current for your big mystery extra wire
also, in your pic, where are you taking the measurement? - we can't see where the test leads go!
Last edited by LScowboyLS; 09-12-13 at 03:24 AM.
#19
load sensative alt. it should be running at 14.1 volts..
is your alternator charge light on the dash working?
the L wire (one of the wires in the 3 pin plug, look at bottom of alt for pinout diagram) to the alternator should be reading exactly what the B+ (large wire terminal) should be. this is when ignition (reds) is on
or the alt isnt sensing any voltage so then it doesnt know what output to put out..
if the globe is blown on the dash this will cause this too..
plus bench test ya alt at ya local auto elec to be certain the alt is ok too
ps just thought too.. on the factory system i think the alt gets an input from the ecu.. so the capacitor issue might be the prob too..
is your alternator charge light on the dash working?
the L wire (one of the wires in the 3 pin plug, look at bottom of alt for pinout diagram) to the alternator should be reading exactly what the B+ (large wire terminal) should be. this is when ignition (reds) is on
or the alt isnt sensing any voltage so then it doesnt know what output to put out..
if the globe is blown on the dash this will cause this too..
plus bench test ya alt at ya local auto elec to be certain the alt is ok too
ps just thought too.. on the factory system i think the alt gets an input from the ecu.. so the capacitor issue might be the prob too..
Last edited by simrx3; 09-12-13 at 03:37 AM.
#20
Driver
Thread Starter
yes, should be higher, more like 13.8V or more, try these two simple fixes first, before buying a new alternator
● a new battery (not kidding)
● this $15 part from any Toyota dealership (the factory + terminal), p/n 90982-05037 (they get hidden corrosion in the inside, robbing power)
although from looking at your pic, your positive battery terminal is a ways from stock, are you using a + battery cable of at least the factory quality and gauge?
the LS400 alternator is kind of on the edge of what is required, just for the car, if it is stock, that is just 80 amps and doesn't really have any extra current for your big mystery extra wire
also, in your pic, where are you taking the measurement? - we can't see where the test leads go!
● a new battery (not kidding)
● this $15 part from any Toyota dealership (the factory + terminal), p/n 90982-05037 (they get hidden corrosion in the inside, robbing power)
although from looking at your pic, your positive battery terminal is a ways from stock, are you using a + battery cable of at least the factory quality and gauge?
the LS400 alternator is kind of on the edge of what is required, just for the car, if it is stock, that is just 80 amps and doesn't really have any extra current for your big mystery extra wire
also, in your pic, where are you taking the measurement? - we can't see where the test leads go!
This is the trunk but I did the front the same way as far as the leads.
#21
Driver
Thread Starter
load sensative alt. it should be running at 14.1 volts..
is your alternator charge light on the dash working?
the L wire (one of the wires in the 3 pin plug, look at bottom of alt for pinout diagram) to the alternator should be reading exactly what the B+ (large wire terminal) should be. this is when ignition (reds) is on
or the alt isnt sensing any voltage so then it doesnt know what output to put out..
if the globe is blown on the dash this will cause this too..
plus bench test ya alt at ya local auto elec to be certain the alt is ok too
ps just thought too.. on the factory system i think the alt gets an input from the ecu.. so the capacitor issue might be the prob too..
is your alternator charge light on the dash working?
the L wire (one of the wires in the 3 pin plug, look at bottom of alt for pinout diagram) to the alternator should be reading exactly what the B+ (large wire terminal) should be. this is when ignition (reds) is on
or the alt isnt sensing any voltage so then it doesnt know what output to put out..
if the globe is blown on the dash this will cause this too..
plus bench test ya alt at ya local auto elec to be certain the alt is ok too
ps just thought too.. on the factory system i think the alt gets an input from the ecu.. so the capacitor issue might be the prob too..
#22
Lexus Champion
Aftermarket remans aren't known for quality or consistency - AutoZone uses Delco-Remy as their remanufacturer and their non-GM/non-AC Delco remans use cheap parts. I'd get a Denso instead.
Get the battery checked too - bad batteries cause alternators to work harder and die quicker.
Get the battery checked too - bad batteries cause alternators to work harder and die quicker.
#23
Lexus Champion
And if you're running two batteries wired in parallel, I'd run an isolator to keep things charged properly.
http://www.oreillyauto.com/site/c/de...0356&ppt=C0061
http://www.oreillyauto.com/site/c/de...0356&ppt=C0061
#24
Lexus Champion
And if you're running two batteries wired in parallel, I'd run an isolator to keep things charged properly.
http://www.oreillyauto.com/site/c/de...0356&ppt=C0061
http://www.oreillyauto.com/site/c/de...0356&ppt=C0061
#25
Driver
Thread Starter
Back from Autozone. They said the alt is charging but not at what it should be and also said the regulator was bad. Are Duralast alternators junk for our cars or could it be the ecu making the alt appear bad? I don't see any point in replacing a new alternator with the same one just to have the same problems happen again. They also said the battery is only at 75%, but that is the alternator causing that.
Any of these any good?
http://www.ebay.com/itm/Lexus-LS400-...0f0911&vxp=mtr
http://www.ebay.com/itm/LEXUS-ALTERN...612299&vxp=mtr
Any of these any good?
http://www.ebay.com/itm/Lexus-LS400-...0f0911&vxp=mtr
http://www.ebay.com/itm/LEXUS-ALTERN...612299&vxp=mtr
#26
Lexus Champion
Back from Autozone. They said the alt is charging but not at what it should be and also said the regulator was bad. Are Duralast alternators junk for our cars or could it be the ecu making the alt appear bad? I don't see any point in replacing a new alternator with the same one just to have the same problems happen again. They also said the battery is only at 75%, but that is the alternator causing that.
Any of these any good?
http://www.ebay.com/itm/Lexus-LS400-...0f0911&vxp=mtr
http://www.ebay.com/itm/LEXUS-ALTERN...612299&vxp=mtr
Any of these any good?
http://www.ebay.com/itm/Lexus-LS400-...0f0911&vxp=mtr
http://www.ebay.com/itm/LEXUS-ALTERN...612299&vxp=mtr
#27
Lexus Champion
What you want is a Denso First Time Fit reman. Yes, stock amperage. But a lot of non-Denso remans aren't that great. You could also try swapping in alternator off an newer Land Cruiser or LX.
#28
Lexus Champion
with the huge cables he has for what are apparently some high current accessories, he seems like the perfect candidate for a high output alternator, especially when it is cheaper than most, these are reman Denso, and the seller seems to have exemplary feedback, and claims to have been a rebuider since 1957, so they are not likely Chinese junk.
I don't see how anyone can expect to run a big high current sound system or whatever and stay with the stock 80A alternator, this makes no sense, electrical engineering-wise!
#30
I am a huge fan of Denso quality, as you well know, but the stock 80 amp alternator is just barely enough for the LS400 when a lot of accessories are simultaneously in use!
with the huge cables he has for what are apparently some high current accessories, he seems like the perfect candidate for a high output alternator, especially when it is cheaper than most, these are reman Denso, and the seller seems to have exemplary feedback, and claims to have been a rebuider since 1957, so they are not likely Chinese junk.
I don't see how anyone can expect to run a big high current sound system or whatever and stay with the stock 80A alternator, this makes no sense, electrical engineering-wise!
with the huge cables he has for what are apparently some high current accessories, he seems like the perfect candidate for a high output alternator, especially when it is cheaper than most, these are reman Denso, and the seller seems to have exemplary feedback, and claims to have been a rebuider since 1957, so they are not likely Chinese junk.
I don't see how anyone can expect to run a big high current sound system or whatever and stay with the stock 80A alternator, this makes no sense, electrical engineering-wise!
totally agree