Few weeks ago my battery light on the dash starts blinking off and on intermitintly. After a day or so of this the car then shuts down while i was driving it at night. Everything goes dim, lights shut off, car loses its power steering and car dies. so i take the car to my brother after he gives me a jumpstart and he decides to put a new alternator in it, because he said the battery was fine.

So after a few days of the new alternator in, the batery light starts flashing on and off again. The car dies on me again in the same way. So then i put a new battery in it.

After about 4 days of no problems other than the batery light flickering on and off, and the dummy lights in the dash going off and on, the car again dies on me. its like complete electrical failure. the car is a 92 sc300, i took it to get the a diagnostic check, but they cant read it.

i dont know how or what to even begin with when i take this to a mechanic. i dont have allot of knowledge about the mechanics of this car. and im trying to avoid being charged 10 hours or more of labor for a mechanic to poke around to figure it out.


the car is sitting dead in my driveway now and im sharing my wifes car now for 2 weeks.
do any of you have a clue what this could be? any advice would be much appreciated

 

OP, it sounds A LOT like a charging system problem to me. I've had this happen before on other, non-Lexus cars and it happened because the alternator was not putting out enough voltage to keep the battery charged ... which caused the battery to have to supply current (vice the alternator) to the engine and rest of the car. Once the alternator was replaced everything was fine. Are you absolutely sure that the replacement alternator is good? Did you have a charging system test done on the car?

I have a little widget that I use for my Nissan truck that lets me know the status of the battery and the charging system and it hasn't failed me yet.

 

This is an exact sign of a bad alternator, a battery is not designed to run your car mainly for cranking, the alternator is what really supplies the car of power, yes you can putt around on a fully charged battery for a bit but not long at all before its drained again. You really need a sufficient alternator to keep that battery charged and systems at go.

 

Check the connection between alternator and battery.

 

Bad alternator. Or loose wire to the lug.

 

thank you so much for the replies, i will get the alternator tested, and check the connections.

 

Autozone may still check these for free in Arizona.

 

Autozone has a handheld device tester that can test both the alternator and the battery and tell you which one is bad. Find someoneway to tow it there if you have to and jump start it so it runs. Obviously if it passes the test for both components, your going to have to run a diagnostic test, even if it fails to show which sensor is bad, it can eliminate what is good. This definately sounds like an electrical issue. Why not get a user manual and look at the electrical schematic?

 

start ur car and disconect the positive terminal from ur battery. if the car shuts off its ur alternator. easiest way to check from home.

 

Your alternator works on a circuit. With this in mind, be aware that IF the alternator tests good THEN you may be showing all the signs of a bad alternator BUT the problem may be somewhere else on the circuit, EFFECTIVELY (and erroneously) giving you the same symptoms of a bad alternator.

If the alternator tests good... To begin, you will want to check:

a) The 3-wire plug that feeds the alternator's IC rectifier and voltage regualtor with control voltage. One wire is 12v live, the other is 12v ignition, and the other is 12v sensor (that I believe runs on a different circuit through the low battery warning in your dash. I believe that all of these should output 12v at the plug if the ignition is set to 2nd position. ALSO make sure that this connection is well insulated. If there is any exposed wiring here, especially near the plug, then some arcing might be happening and causing the alternator to behave differently (i.e., not wanting to output the required voltage to the battery...)

b) Check your ground, especially the one immediately behind the battery. It's easy to find... just follow your battery negative cable down about 1 foot and you will find that it is grounded there at the chassis by a 10mm bolt. You may want to unbolt it, clean both surfaces with sandpaper or something, rebolt, and coat with dielectric grease or a battery terminal sealant spray.

Hope one of these thing helps you!

 

BTW, if you need a new DENSO 3-wire alternator plug, Autozone is the only auto parts store that carries them. They cost $13.99 and it's a 2 day wait for ship to store.

 

Ditto what others said. Check all the wiring connections for tightness and corrosion. I have actually cut open battery cables and found the entire inside covered in corrosion inside the jacket. Battery cables aren't meant to last forever. I've also seen fusible links go bad internally as well.

 

YES! I forgot about this one. Check your 150A (or 120A... not sure of the exact value) fuse under the hood. It's the big square one at the passenger front corner of the fuse box. Also check the fuses in the smal fuse box under the dash by the driver's footwell. There should be 3 fuses that interact with the alternator... I can't think of which ones off the top of my head but you should be able to figure it out by looking at the inside cover.

 

I had almost the exact same symptoms when I first bought my SC. The alternator being the culprit, a battery and an alternator later, the problem was gone.

Like others have said, your replacement alternator could be faulty, bad/poor connections, fuses, etc. When you get the alternator tested, ask what the voltage reading is (after the alternator should have had time to charge the battery- if it is). When I went to have my alternator tested it showed up in the auto parts store's tester as fine.

 

Good info guys. I won't add anything to this. Guys said it all.