1992 Lexus electrical problem

My wife was driving home from work yesterday and suddenly several of the warning lights came on. The battery, brake, tail light, temperature and oil lights all came on at the same time. I thought maybe she had a weak battery but when she got home it seems to be fine, although I don’t have a way to check it other than it will crank the car with no problem. The battery is 13 months old and it is one of Interstate Battery’s best. I have replaced the alternator with a rebuilt one about 2 years ago.

A couple of things I noticed while working on the car last night is that if you put a load on the electrical system while the car is running the light will go out. Turning on the headlights won’t make them go out but if you also hit the brake or turn the blower fan to high while the headlights are on they will go out.

Another thing is that the lights don’t come on as soon as the car starts, it takes about 15-20 seconds for them to light up. Also, there dosen’t seem to be any problem with the power to the engine, the car runs fine.

My question is do you think I have a bad alternator or is there something more to the story?

Thanks for your help!

Something else wierd about the lights is that when they come on after you start the car they flicker a few times before they stay constantly lit. Also, I forgot to say that the car is a Lexus LS400 automatic.
I mentioned earlier that I thought it might be because of a weak battery only because once when the cars alternator went out and the battery was drained while we were driving the car, just before the car died from loss of power the warning lights did this random flickering.
Anyone have a clue what it might be?

We have a lot of clues. See how those battery terminals look. If they look like they’ve lived too long, you might want to clean the contacts a bit. If you can twist it by hand, you might have found the problem. Loosen and retighten the ground wire from engine to fender. Check the battery voltage. If it doesn’t show at least 12.5, you can wonder about it. Don’t you ever use an Interstate battery in a Lexus again, although you might have the good one. Odd electrical problems are sometimes from a bad connection. It really sounds like a bad connection or a corroded cable. Check for insulation cracks on the negative cable. If the manufacturer is going to cheap out, it will be on the negative one. If the detents in the ignition switch are vague or it gives the feel that the switch has sand in it, your problem could be there.

The ignition switch has the symptoms of a worn out switch. The connecting linkage between the ignition lock, and the ignition switch (the part with the contacts and wires), could be worn so much that it allows the key to be removed with the ignition switch contacts still in the RUN position. A good idea would be to replace the ignition switch (the part with the contacts and wires), and have the connecting linkage checked for excessive wear.

Those warning lights you mention may be in the alternator exciter circuit and is a common design. When the alternator has a problem the lights will turn on. I think if you replace the alternator it will fix the trouble. Have it checked out before replacing it to make sure. I think a load test on it will do the trick.

I just wanted to say Thank You to everyone who replied to this post and to let you know what the outcome was. I took the car in and had the charging system checked and it turned out to be an over-charge condition that was causing the problem. The alternator, which was only about 1 year old by the way, was putting out nearly 19 volts to the system! That would explain why I could put a load on the electrical system and it would make the warning lights go out. One new alternator and about an hour flat on my back later and the problem is fixed!

Glad you got the car fixed. It would have helped when you said “lights went on”, or “lights went out”, that you had specified what type of lights you were referring to. Some of us thought you meant lights controlled by various switches; but, no, now we find out that you meant some indicator, or warning, lights. Some way, Cougar picked up on which type of lights you meant: warning. Congratulations to Cougar for that deduction.

Thanks Hellokit. It really wasn’t a big deduction on my part. He talked about the warning lights in his second sentence of his original post. I just figured those were the ones he meant in his second paragraph, before mentioning the headlight.