Is my alt bad?

[fatryan 5,000+ posts]

ok, i just upgraded my BIG 3 to 0awg wire. Ever since ive owned my blazer, the instrument cluster bat gauge has read ~12V at idle (it reads ~14 at anything other than idle). i got this 160 HO alt about a year ago and it had no affect on the V at idle. i figured it was cause i never did the BIG 3 yet. well its all done today, and the **** thing is still reading ~12V at idle (from instrument cluster gauge). i checked it with a V-meter, and it seems to be reading ~14V at idle (but my V-meter is old and weird, not even sure if its working correctly). well, i would normally say that my cluster gauge is just wrong, but i also notice that the lights are dimmer when at idle too. what the hell is going on here? is my alt bad or something (maybe not set right)?

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[cobra133 10+ year member]

Don't worry about its, most alternators dont do 14V at idle with amps running.

 

[Decipha 10+ year member]

thats a minor problem that i wouldn't even consider a problem just as long as everything works fine and the car doesn't lack power when the radio is on at idle don't worry about it... but if you do have power problems you can idle your vehicle up a little... is it idle'd low right now? Also i knew this guy that had an old school 79 cutlass and his car did the same thing.. He took out the alternator and put a new flywheel on it that was about half the size of the one he took off. That solved all his problems.

 

[datguyclark 10+ year member]

14v at idle is normal, but take it to advanced or somewhere that does a free alt check and u can get a printout with the loads on it and see how many volts and amps it is pushing and also check the diode pattern, but chances are those crappy gauges in the cluster are wrong...very common

 

[fatryan 5,000+ posts]

no, its at ~12V at idle with NO radio, AC, lights, wipers, etc. thats why im worried. my truck idles at ~700 RPM

 

[fatryan 5,000+ posts]

14v at idle is normal, but take it to advanced or somewhere that does a free alt check and u can get a printout with the loads on it and see how many volts and amps it is pushing and also check the diode pattern, but chances are those crappy gauges in the cluster are wrong...very common

but then why are the lights dimmer at idle?

 

[mobileaudio219 10+ year member]

At idle your car/truck should be running at around 13.8 - 14.0v.

It's probably just a crappy gauge, but have it checked out to be sure.

 

[Naxis2k1 10+ year member]

i had the same problem with my ho alt. thing is most ho alt dont turn on until 800-900rpm so you will only get 12v at idle. only thing you can really do is find a alternator with a really low rpm kickon rate. or up the idle speed witch i dont know if that would have any other effects on your car. only thing i notice that happened to my in my case was my alternators would go bad very quickly. always was the internal voltage regulator that got messed up. i guess the alternators didnt like going from 12v to 14v every stop.

 

[fatryan 5,000+ posts]

well my truck idles from 600-700 rpm, that seems low. HO alts dont really "kick" on. theyre wound for higher amps and some have smaller pullys, so its all a matter of rpm. but its not really a big deal i guess. id just prefer it to be at 14V as often as possible.