hey guys

yesterday i was driving my car around my neighborhood when all of a sudden i look down and see that on the dash, the brake and battery lights are both on. i reved the car up and the lights went out. it proceeded to do this the whole way home.

i get home and shut the car off, and try to start it again, it starts, i shut it off.

i get my DMM, and check the battery. 12.3 full is 12.6, which it should be casue the alt should be charging it.

i then start the car and let it run for about 15 min. the alt should be charging it, therefore the battery voltage should be higher, i checked it at 11.8.


also, what is the best way to get the alt out of the ka24e??

TIA
Matt

 

id say once you get it off take it an autozone or something and get it checked out.

 

best way to check to see if your alt is bad is to start the car and then disconnect the battery. the car should still be running if the alt is still good. the battery is to power the starter for initial start up and other small electronics. after start up, it's all up to the alt. if the car dies right after you disconnect the battery then it's the alt. it's not hard to pull the alt. good luck

 

Pick n Pull sells used ones for like 20 bucks. They're easy to get out.

 

i really really recommend not to disconnect you battery when the car is on EVER the battery is what protects your electronics in the car it dampens voltage spikes from the alternator and its very bad to disconnect the battery with the car on.

 

its the alt

 

Battosaii, if the car can run without the battery wouldnt that mean any voltage spikes can go around the battery anyways? Regardless, he said it was reading 11.something volts. Taking the battery out for 2 minutes won't hurt.

 

no cause the alt runs the car and charges the battery w/o a battery to charge it will make too much power and there isnt anything there to dampen voltage spikes.

 

No, the alternator won't make too much power. Thats what the voltage regulator is for. If it goes out the car will overcharge with or without a battery.

 

but still the battery is a Dampener w/o a batt you can and will f up your electronics might not be immediately but it will happen this is what Dealers call "job security"

 

The only way that it will screw up your electronics or ECU is if you disconnect the positive post before disconnecting the negative post.

 

no lol.. ok fine believe what you want i went to school for nothing then and i shouldnt be a mechanic cause you all know more then me hey maybe they should take away my ASE's w/e..

 

I actually think Battosaii is right, but what I'm saying is whats the probability of any harm if the car is idling and the battery is only disconnected for like less than a minute? Anyways, i guess the best thing to do would be get a multitester and test the alternator output.

 

OK there is no such thing as dampen voltage. Take it from me I am a degreed electrical engineer with a degree in electronics too.

The alternator is merely an electric motor that gets spun the opposite way. And when spun by the motor via the belt the alternator creates AC voltage. But also build into the alternator is a rectifier that takes that AC voltage and converts it to DC, and a voltage regulator circuit to suppress higher voltages. There is a voltage regulator the does "clamp" voltage spikes, and transient voltages. The battery, the output from the alternator, the voltage regulator, and the load (your car and everything running off of electricity) are all connected in parallel.

Now the function of the alternator is to recharge the battery after starting, and to run everything while the cars in use. The battery is there for starting and memory items only. (Granted if you have a stupid system) then the current draw may be more then the alt can supply and then the battery would supplement the current flow until it died or the draw went away then it would recharge. This is why the kids with systems burn up alternators, need second batteries, and caps.

The best way to test to see if you alternator is bad is turn on your lights, radio, interior light and disconnect the battery while the cars running. Just be careful not to short anything. If the light go really low or the car shuts off you need an alternator.

 

taking the neg cable off whice the car was running was the test method i used. and just to make sure that it was a reliable method, i tried it on my good running grand prix. the 240 died and the gp did not.