damnit. my car idles beautifully at 750rpms. as soon as my headlights are turned on... BAM idle drops to like 400rpms. it will hold the idle but damnit it's annoying! what could be causing this. dont worry i know to search as i did. found nothing on this subject. think i have bad grounds? i do have an fc alternator. my car has always done this i think but now it's noticable since my car idles correctly.

-zac

 

Sounds like your alternator is drawing a lot of engine power, causing it to bog down. Is your battery OK? If it isn't, your lights are drawing all their power (or at least most) from the alternator, putting more strain on it and causing it to use more engine power to spin it.

 

zac, also check your grounds. the one to check would be the one on the left strut tower that is for the negative battery cable. i do agree with 85rotarypower on the high amp draw from the alternator. the added draw put on the engine by a bad alternator will definatly cause an engine to drop its revs.

 

so you think it's a bad alternator? it's fairly new. my battery is pretty crappy. i'll check that main ground tomorrow. oh yea mazdaverx713b; i got the imsa bumper off today. lol

 

i allso think that it would be the batary thats not taking the all the load it should be taking cause it cant store up the power to run your lights and stuff id take a voltmettrer and make shure its getting from 13.3V to 14.5 V

 

I have exactly the same problem. Took it too a auto-electrician and they did a few things. It helped but I really need a new alternator. My car won't brap with the lights on, and the idle drops about 200rpm.

 

convert to a buik alternator
120 watts of jiuce

 

Upgrade to a s4 - s5 alternator, 85watts output against the standard 55. Only thing is you'll have to change the pins to fit, which any good auto elec will do for like $10

 

i have an s5 alternator. it doesnt have many miles on it either.

 

ummm .. isn't amps, not watts ??

 

well, depends what you're measuring. Current is measured in Amps, power in Watts. Power=current*voltage. Current refers to the flow of electrons only, whereas power says more about the total energetic capacity of the system in question.
There's more to it than that, but that's the jist of it.

 

so, are you going to be selling the bumper

 

Well what he meant to say is 120 Amps of juice. Alternator's aren't designated by their wattage, only their amperage. So your silly stock alternator is putting out 60 Amps Max.

 

which again, i dont have. i have an s5 alternator. and yes (mazdaverx713b) i would like to sell it. but not sure how i will ship this thing. it's pretty big. hahaha

 

thx