My93 LS400 has give up the ghost and it all points to the alternator. The belt and power steering pump are fine and am confident the battery is good. Symptons are when I start the car warning lights go out as normal. When the cold start cuts out the revs drop and all the warning lights come on. They go out at 1250 rpm. It's possible to use the car by day but not by night. The car sarts fine unless I have run it with the warning lights on. Am I barking up the right tree with the alternator or is there something obvious I'm missing?

 

Welcome to Club Lexus,,,,,

Sounds like you have pin pointed it right, most likely the alternator. Is the battery still good?? How old is it?? But in all probability it is the alternator. If you haven't already done so, fix the leak in the powr steering pump, as it sits directly over top of the alternator and has a tendency to leak dirctly into it, and eventually kill it. This is a common problem with the entire LS line and t will save you from having to replace another alternator pre-maturely later. Problem can be resolved by either capping off the lines or by replacing a small part called the Idle Air Control Valve ($120 from dealer only). Threads relating to this problem can be found here by using the search and advanced search feature and just putting in the key words.

 

I've ordered the alternator and will post if it cures it. Will keep an eye on the PS pump, it's dry at the moment.