93 corolla battery warning light need help

[freemee22]

hi, did a search on this and didn't find the answer, need some help regarding battery warning light on the dash. When I start the car the battery warning light stays on, while the engine is running I detached the battery cable negtive side and the warning light goes out and the engine is still running and when I connect the battery cable while the engine is running the battery warning light comes on. What could cause this trouble? The alternator is new (do you guys think I got a bad one? it is from pepboys) and I have the battery checked and it was good and I put in another battery with the same result, checked all fuses and they are all ok. It is a 1994 1.8L. I measured the voltage around 12.5 volts with the engine not running and when it is running around 14.5 volts didn't get the amperage reading.

anybody have any suggestions as to how to trouble shoot this is greatly appreciated
thanks

[freemee22]

anybody??

[tashirosgt]

Did the light start coming on after you put the new regulator in? I don't have a manual for the '93 handy, but you should be able to look up the charging voltage. 14.5 V might be a high, but one never knows until the manual is consulted. If the voltage is too high, this usually indicates a bad voltage regulator. The regulator is often built into the alternator - another thing the service manual would tell you.

[freemee22]

actually I made a mistake the car is a 94 , but to answer your question Ichecked the service manual and 14.5 volts is good. The light has come even before I change the alternator. I changed it cause I can run the car for 15 mins with the old alternator with the battery unplugged but after that the car would die. Since the alternator was under warranty from pepboys I had exchange cause the alternator was deing after 15 mins, now with the new alternator it is not doing but as soon as I connect the battery the battery warning light will come on, don't know what is causing this .

[REN69]

In other words.. the Alternator is fine.. sounds like the battery might be dying, borrow a good battery from someone and see what happens OR take your battery to pepboys and get it checked, usually if you take one of the cables off from the battery and the car still runs it means your alternator IS good. If you took the cable off and the car died, then the alternator is not strong enough to keep the car running anymore.

[retiredat44]

Take the car back to PepBoys and have them throw it on the tester machine, test the whole charging system. Also, how old is the battery? if it is older and 3 1/2 years I would think about that. Most won't give you more than 4 years.
You can get bad Alternators, I got a bad one (Bosch) from Pepboys last go around, in fact it blew all the charge fuses, they actually exploded in pieces, I suspect the Alternator rebuild house they get their alternators from put the wrong parts in or reversed the polarity... in any case I had to take the new one off and they gave me another new (rebuilt) and it was finally fixed, but had to replace the damned charging fuses as well. (those are huge amp fuses! .. they didn't go silently they exploded!)

[freemee22]

thanks for the response, I had the battery checked and it is fine don't know how old the battery is but it is an interstate battery but still I went ahead and put in another battery and the result is still the same, battery warning light is on when i start the engine and when i took the negative lead on the battery off , the engine is still running and the warning light is off, don't really know what is going with this

[REN69]

Try maybe resetting the ECU then.. take out the ECU fuse for a couple of hours to reset and see if this takes the warning light out. If not.. don't know what to say.. maybe a bad connection somewhere.. if the car still runs fine, I probably just forget about it.

[freemee22]

doesn't it reset the ecu when I took the battery out ? I took the battery out to get it tested and I took the battery out too when I put another battery in. Or is there another way to reset the ecu?

Thanks

[REN69]

Depends on how long you had the battery out.. I believe the ECU would take a couple of hours to reset. The only other thing I can think of is the negative wire going to the alternator, my dad's Toyota van had a similar problem and it turned out to be bad ground wire.

[freemee22]

how bad was the ground wire like open ?

[AVANT]

If the problem is grounding related, any grounding wire only has to be slightly loose to give you symptoms.