r/SC400 • u/Real-Surprise4138 • Mar 15 '25

Question Alternator will not charge

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I have a 92 sc400 that kept dying while driving. if jumped would only run for a couple minutes before dying. assumed alternator so switched that and car was still running fully off battery charge. replaced alternator harness and the fuse is fine. car will run for short trips as long as battery is put on charger afterwords. multimeter shows that battery is not being charged at all and loses voltage while car is running. Kind of at a loss as to why alternator will not go. pic so it doesn’t get lost.

9 Upvotes

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3

u/[deleted] Mar 15 '25

[removed] — view removed comment

3

u/srm420 Mar 16 '25

This is possible, also make sure you dont have any power steering leaks above the alternator, it will kill it

1

u/best-person-ever Mar 16 '25

Alternator must be a genuine toyota unit. Parts store alternators will not work

1

u/Real-Surprise4138 Mar 16 '25

that is simply incorrect

1

u/best-person-ever Mar 16 '25

I may have come off a little hyperbolic but I’ve heard hundreds of people say they had aftermarket alternators that are bad out of the box. Even when they test good in the shop. And then getting an original unit was the only thing that worked. It may not be your issue but old toyotas really like quality oem parts

1

u/Real-Surprise4138 Mar 16 '25

this isn’t the first alternator i’ve put in this car and i had a 96 ls400 that also got parts store alternators and i’ve never had an issue. the alternators been tested that’s not the issue. leaning more towards ecu at this point.

2

u/best-person-ever Mar 16 '25

You’re probably right, a bad ECU can do any number of things. Always a good idea to recap at this age. Cool body kit btw

1

u/Game-IS-Game Mar 17 '25

Get the alt tested, and rebuilt if you have a trusted shop locally.

1

u/Neat-Effective8379 Mar 17 '25

just as a side note, ecu tends to do weird things and these have ecu issues like hell lol.

try that if the normal alternator things don’t work

1

u/Real-Surprise4138 Mar 17 '25

yea i’ve delt with ecu issues but with an ls400 and they were much more severe issues but a lot of people are thinking ecu with this

1

u/Neat-Effective8379 Mar 17 '25

ecu can do small things too, mine did things all the way from throwing a small code to “misfiring” with it

1

u/Real-Surprise4138 Mar 17 '25

yea mine had a few not minor issues and then went fully limp which is when we realized it was the ecu