Need Help! Alternator Problem

[Carvasarus]

I own a 1997 LS400 270,000 miles. In June replaced a leaky power steering pump. Shortly after alternator went bad. I removed the alternator and had my local shop rebuild the original alternator. After a couple of months car does not start. Take it into the shop and the diodes are blown. Shop rebuilt the alternator again for no charge. Two weeks ago car would not start again. Take it back in the alternator is bad again shop rebuilds again no charge.

This time they notice that when they have it on the charging tester that when the brakes are applied there is a big draw down on the alternator. Thereafter, I take it to another lexus repair shop and they state that it is the wrong alternator. Could there be an electrical short that is blowing out the diodes in the alternator or is it another problem.

Thanks for any help.

[93ls400walt]

The ls has a large amp alter. I believe around 100 amps. if your shop did not rebuild according to the amp flow the replacement parts may not hold up.

The earlier year ls has a problem with the wire harness on the drivers side trunk hinge. Specifically at the sharp bend of the harness. Where the wires tend to break. This causes many strange problems with lights, trans shifting ect. Most worse when the brakes are applied.

[Carvasarus]

The ls has a large amp alter. I believe around 100 amps. if your shop did not rebuild according to the amp flow the replacement parts may not hold up.

The earlier year ls has a problem with the wire harness on the drivers side trunk hinge. Specifically at the sharp bend of the harness. Where the wires tend to break. This causes many strange problems with lights, trans shifting ect. Most worse when the brakes are applied.

Thanks, is the wiring harness easy to inspect?

[eatingupblacktop]

If the alt has been rebuilt a couple of times without being tested and no report after the first failure, then the shop's work is suspect. They should have bench tested the alt after the first rebuild and given you a report. Get a Lexus/Toyota dealer to do a load test on the alt and have them give you a print out of the results. That'll tell you if the alt has been rebuilt properly and whether it has the required output. It's also possible that if you didn't buy the car new, the alt has been replaced before you purchased it with an aftermarket/used one that is under spec.

[SKperformance]

If you have a large VCD load when braking , it is a lighting issue causing it to fail so fast.

check the trunk wiring as previously mentioned.

[Carvasarus]

When I am inspecting the trunk wiring harness, where and what do I look for.

Thanks

[90LS400Lexus]

I thought only the 1990-94 LS400s had the trunk hinge wiring harness woe?

Could be wrong though.

If yours is like the first generation models, its the wiring harness thats on the left side trunk hinge. Apparently the wiring gets twisted and frazzled and causes strange electrical gremlins to pop up.