Hey all;

Recently the battery light on the dash lit up but there's no check engine light. I replaced one of the ignition coil packs a week ago due to a misfire code. Car's been driving fine ever since. The alternator was replaced in February, battery is only a couple years old.

I know the battery light refers electrical but shouldn't the check engine light ignite and blow a code for me as well?

Thanks,

 

Depending on what year it is that car uses a generator not an alternator. Alternators have internal voltage regulators. Generators have external regulators. The voltage regulator is incorporated into the PCM on that car I'm afraid.

 

Sorry. It's a 2002 Mazda Protege5, 2.0 ltr engine, alternator, was replaced in Feb. Battery light went out and hasn't come back on so I'm thinking there's a short somewhere.

 

Sorry but the regulator is in the PCM on that one. I realize everybody calls it an alternator but it is in fact a generator. No biggie. It could be a bad generator or it could be a bad PCM. You need an oscilloscope to properly test it. The lg/v (light green with violet tracer) and v/l (violet with blue tracer) go to the PCM which control voltage output based on electrical load.

 

Thanks for the info. Just wasn't sure how serious it was since there was no check engine light. Last time we had a check engine light come on with it. Seems to be holding a charge and it's still intermittent. Guess I'll book an appointment. The generator was replaced last year around the same time, but I can't remember if it was new or rebuilt, maybe it's shot.

Appreciate the help!

 

i would bet it has to do with the plug in wiring on the back of the alt. as the other person who posted mentioned,the alt (or generator,as he referred to it) is definitely computer controlled.

any decent mechanic should be able to test out the wiring on the back of the alternator.i think the " plug in" wires are what actually goes off to the computer to trigger it to turn the voltage regulator on and off....

some stuff you can maybe check for.....

how good of shape is the belt in ???? any chunks out of it,or alot of cracks???

the belts on these generations of proteges get not looked at much as they are kinda hard to see and rather pain to get changed out. The belt is a "trapped style" of belt too,meaning the other belt ( power steering and a/c belt ) is in front of it and has to be removed to replace the alternator belt.

the power steering and a/c belt on mine was new and was recently replaced " i think " mainly to get the a/c working and such....

my alternator belt, which was still on the car and was still use-able,was missing an inside rib and some chunks were missing from it as well. car was ok and ran fine with that belt until the alternator locked up on the car.....
that removal was the first time i had to remove and replace that bugger,( through the top by the way ),i took it to a local alternator and starter place and he fixed it for like $35.....

2 weeks later the voltage regulator inside of it went out, and in and out the alternator came the second time.....

i can currently do the whole job ( take it out and put it back in ...) in around an hour, if i don't have to go out for stuff....yeah,fun times.....

on a side note, i have never seen under the hood of the p-5,so i don't know how much different they are from regular proteges....

after all that above.....

i bought ( off of ebay ) a few of those plug in style voltage "gauges".....they plug in to the cig lighter and show the voltage as the cars system actually sees it.... i think they were a whopping $ 2.12 with free shipping to the u.s.a......not really a huge investment,but kinda nice to have....