LS400Convert Posted June 30, 2003 Share Posted June 30, 2003 I have owned a 90' LS400 for about 2 years. It has been an awesome car, but now I am stumped. On a particularly hot day, I drove the car a few miles, shut it off, restarted after a few minutes and all warning lights remained on on the dash but the engine was running fine. As I was driving it became apparent that my dash lights were dimming and my fan on the air conditioner was running slow so I then thought I had lost the alternator and had been running on the battery. I normally would replace it myself but I didn't have the time. I called the Firestone place to come get my car and replace the alternator and serpentine belt. When they came to get it (I wasn't there) they said it started right up and they drove it to their shop. They didn't replace anything since they couldn't find anything wrong. When the car cools down completely it will start and run fine whether you drive it 1 mile or 100. But if I shut it off and then get back in and drive, then all the lights come on and I assume once again that I am running on battery power only. I put in a brand new battery a few days back and it didn't help. Could it be the computer? Thanks for any help you might offer. Quote Link to comment Share on other sites More sharing options...
mig25 Posted June 30, 2003 Share Posted June 30, 2003 ;) It is just a Thought, but you might have an overheating problem, make sure you keep an eye on the temp Gauge and see how high it gets. I also own a 1990 LS400, I recently flushed it's cooling system for the summer and replaced the thermostat. Some of this high tech cars tend to run bad and most of the times they shut off completelly when overheating. Again it is just a thought... ;) Quote Link to comment Share on other sites More sharing options...
SKperformance Posted June 30, 2003 Share Posted June 30, 2003 it is very possible to be the alternator check to see if the power steering pump is leaking on to it which causes an occasional problem also make sure the secondary battery connection after the terminas are secure i don't think it is an overheating problem as you would have the issue before shut down Quote Link to comment Share on other sites More sharing options...
LS400Convert Posted June 30, 2003 Author Share Posted June 30, 2003 The power steering pump did leak when I first bought the car. I fixed it with Power Steering stop leak but there is no telling how long it was like that before I bought it. Thanks for the idea, I will check it out. Quote Link to comment Share on other sites More sharing options...
spiller91ls Posted June 30, 2003 Share Posted June 30, 2003 Are these the light's that come on in your instrument panel: low oil level, low coolent, battery, parking, tail light out: if these are the lights that are on then your alternator is bad, when the alternator gets hot enough then something in the regulator opens up. My did the same thing to me last week on the way back from california I trouble shoot it for about two hours in which time it cooled down enough for me to ge back to New Mexico, I was traveling at night. when I got home I found a wiring print from a friend of mine who is a mechanic. and all those lights are hooked up directly to the yellow wire coming from the alternator, and go thru several dioeds, so instead of just the battery discharging light coming on, all those lights come on. probably lexus's way of making you go to them and replace the alternator for big $$$. Mine cost $229 from Checker auto, they have on for $175 made by autolite but I don't think it has the pulley installed on it. should get it tomarrow, and today i'll get under in to pull it out. Try one other thing on it, this is when I first noticed it, press your gas pedal down to the full throttle button and see if you can make the lights blink off/on, also your cruise control won't work if all the light are on. Quote Link to comment Share on other sites More sharing options...
LS400Convert Posted June 30, 2003 Author Share Posted June 30, 2003 Thats exactly what mine did. Including the blinking under heavy acceleration. Like you said, it has all the symptoms of alternator, but usually when I have had alternators go out on other cars, they just quit and thats it. This one has something that reacts to the heat. Anyway, thanks and I will let everyone know if that fixes my problem. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted July 1, 2003 Share Posted July 1, 2003 my es has a weird one also they alternator is crap at idle only 12 volts but jumps after 1200rpm which is kind of normal but still doesn't give the right amperage when hot it is perfect when cold even took it out and to a shop and they opened the whole thing to find a problem and said it works great Quote Link to comment Share on other sites More sharing options...
SRK Posted July 1, 2003 Share Posted July 1, 2003 Many Japanese cars use an alternator field disconnect switch at idle, which eliminates charging drag and improves idle quality. This may accound for the jump in output voltage as you rev the engine. I do not know if the Lexus line does this though. Quote Link to comment Share on other sites More sharing options...
LS400Convert Posted July 11, 2003 Author Share Posted July 11, 2003 If anyone reads this thread, I replaced power steering pump and alternator. The alternator fixed the problem, excellent diagnoses. Thanks for the help. It was about 5 hours labor and $450 in parts that I purchased at O'Reilly. First time I've ever done it on this car and hopefully the last! Quote Link to comment Share on other sites More sharing options...
SKperformance Posted July 11, 2003 Share Posted July 11, 2003 glad the community helped you also i found lexus has made a new sized pulley wheel for my es as to get more juice at idle so i may gety a new wheel but since a changed all the wiring from the battery to the engine i start and run much better than before Quote Link to comment Share on other sites More sharing options...
spiller91ls Posted July 11, 2003 Share Posted July 11, 2003 glad i could help. the alternator took me about 2 hours to change, since i didn't put a new power steering pump in. I did build a shield to go over the alternator so any dripping oil will not get on the new alternator. Last week on the 4th of july my water pump let go on me so i'm in the process of replacing it and the timing belt. it's a pretty easy to do, just a bunch of sensors to remove without breaking any of them. Quote Link to comment Share on other sites More sharing options...
LS400Convert Posted August 22, 2003 Author Share Posted August 22, 2003 I lived in Silver City when I was little, how is it now days? I grew up in Grants. Quote Link to comment Share on other sites More sharing options...
spiller91ls Posted August 23, 2003 Share Posted August 23, 2003 It's pretty nice over here right now, our high are 90-92 degrees and nights a 70-75, and getting rain in the evenings. as far as the neighborhood we're getting a lot of people moving in from california, and that group of people can screw up anything. it's a good thing we have a big mining company out here that owns a lot of property or they would try to fill up the hills out here with houses. Quote Link to comment Share on other sites More sharing options...
ToddLS400 Posted August 23, 2003 Share Posted August 23, 2003 glad i could help. the alternator took me about 2 hours to change, since i didn't put a new power steering pump in. I did build a shield to go over the alternator so any dripping oil will not get on the new alternator. Last week on the 4th of july my water pump let go on me so i'm in the process of replacing it and the timing belt. it's a pretty easy to do, just a bunch of sensors to remove without breaking any of them. What did you build the shield out of? I was thinking of doing the same thing last week. Can you take a digital picture and post it here. I'm very interested. Quote Link to comment Share on other sites More sharing options...
spiller91ls Posted August 26, 2003 Share Posted August 26, 2003 when you remove the alternator you have to remove the shield that is on it to put on the new one, just use that and a piece of sheet metal or aluminum. I made it like a tube just to make sure anything that dripped on it wouldn't get on the alternator. it's been on the car for a couple of month now and i'm not going to take it of to get a picture of it. I changed my oil last week and haven't seen any new leaks on it so i probably didn't need to make the sheild anyway. Quote Link to comment Share on other sites More sharing options...
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