DarlaMG

This is the diagnostic result. My question is should I move forward with the repair or look into other possibilities of why car didn't start one time. No other warning signs are present as in lights dimming or other electronics not functioning.

Tallyhoe

If you don't remedy the power steering pump leak, assuming it's the culprit. You will be in this same situation in a year, as it will leak onto the new alternator and damage it. I've learned this information here, while looking for information about leaks on an SC400. You can attempt a rebuild, there is a how-to guide on this site, and save yourself some money. A dead battery will cause the car to not start, but if the alternator is dead and not charging the battery, then you will constantly have a dead car.
I would ask the shop, if they knew where the leak was coming from and if they could fix it?, and could they maybe rebuild the alternator, if possible?

DarlaMG

Almost all leaks have been repaired. Garage taken to only wanted to replace not rebuild.

Tallyhoe

From the note on your image, it states about the leak. If they repaired that leak, then I would go ahead with the replacement. Here is the guide I mentioned before about the rebuild, if necessary. I would make sure they use a Denso unit, btw.

DIY 1992 SC400 Alternator Rebuild-- - ClubLexus - Lexus Forum Discussion

KahnBB6

iTrader: (5)

Seconding the advice to rebuild the power steering unit *IF* if it is leaking. That is a very common way that an SC400 encounters an alternator failure since a leaking PS pump is right above the alternator on a UZ engine.

Ldepaso

i also had a leaking power steering, alternator was soaked with fluid, not even sure how it was still running but i replaced both those together instead of coming back for a second job a few months later when the alternator will eventually fail. my suggestion is to go with a good brand alternator, like motioned above. i swaped for denso.

DarlaMG

The power steering leak was fixed months ago. Plus the car has started ever since that one time. Not sure the garage that it was taken too was really on the up and up also. I am getting the car tomorrow and starting from scratch. I guess what I need educated on more than focusing on the "leak" is the voltage under load and regular normal for the car? Other than not starting that one time all the normal alternator issues are NOT present.

KahnBB6

iTrader: (5)

It sounds like what happened is that even though you got the power steering pump leak repaired a while back the alternator still had some fluid leak damage leftover from that time... and perhaps it just took this long for it to be affected by it.

Also depending on the age of the alternator it is possible that its internal voltage regulator is just starting to go bad anyway. Denso OEM spec alternators are very reliable but with a lot of age and wear and tear this can happen to them.

I looks like the OE Denso alternator (DEN210-0173) which is a 100 Amp 3-phase model is now discontinued. So a remanufactured or self-rebuilt OE Denso alternator would be the way to go.

There is an alternative however: Denso Model #DEN210-0175 100 Amp alternator for 1998-2000 SC400's. ($260 or so from DensoProducts. Rockauto may also have them in stock).

It uses the same oval plug that your 1995 model uses and with the same max amperage rating will be compatible with your circuitry.

The 1998-2000 SC400 1UZ-FE V8 engine is just an evolution of the same engine in your 1995 model and so this slightly newer alternator will bolt right up to your engine.

Denso is the original maker of OEM alternators for Lexus SC300/400's so this would be an updated bolt in replacement part for your SC400.