Alternator volts way down

My car has a problem where at long stop lights the idle will drop very low to about 500 and then stall... I took a meter and checked my volts on the battery and soon as I started the car they were high 13's then within seconds they dropped to high 12's... then when I put the car in drive with the ebrake on, the rpm's dropped and the volts dropped even lower to mid 12's....I have UD pullies so idk if this is normal for the alternator to do with the UD's but from what I understand it should never drop that low..... Is my car dropping rpm's and stalling at lights because the alternator is giving a weak charge.. also the volts were not steady, they would jump around threwought the 12's from high to low....

also thats signs of a bad alt. right

Do you have another battery you can test it against? I would start with that and see if the battery is actually holding a charge first.

Ira

mm the battery is brannnnnnd new but I can grab another battery and try it out..

I discussed this with him..Ist either a weak alternator or the idle needs to be rasied due to the UD pulleys..Put a post up in the members section

Hes getting low 12 volt range at idle 500rpm (in gear)

13.5 volts at 800rpm in nuetral

That rules out the battery then. I would tweak the idle speed anyway because 500 is too low.

Ira

get a new alternator, yours is bad. mine did the same thing a few weeks ago.

Once the car is running, the battery plays no role (except as a voltage equalizer) in the charging system whatsoever. If its not gettin juice, and the car is running, its a bad alternator.

My '94 auto does something similar. When the warm idle is around 600rpm (in drive) the voltmeter shows a good charge, like 13+ volts; but the needle waivers slightly - enough to make the lights flicker. The alternator is relatively new, but I was thinking maybe the regulator was faulty or maybe needs adjusting. Can they be adjusted ?, does anyone know.

mmm as un updateeee, I adjusted the idle up a little bit, pulled the battery and went through the drive cycles to re-learn ...now in park my idle is around 850ishhh maybe a litttttle higher, and in drive its about 700... compared to the 500rpm->stall i had goign on befor... but it seems to run much smoother, and I do not stall or shudder at lights anymore... not to mention re-doing the drive cycle seems to have made the car run better.... so...

yea false alarm .. car dosent stall anymore but now when i let off the gas i speed down the street at 30 mph in idle...... great

Is it automatic? it could be your torque convertor at idle sticking, try doing this.

adjust idle up to 800-1000 rpm in neutral. in manual or auto. if you get any more q's e-mail me at dyarve@hotmail.com

I never thought about the TC, especially as I put a bottle of Lucas in the trans to help with a small leak (stuff is like Gorilla glue). I guess I'll find out next time I change the fluid.

Re: Alternator Prob

I ran into something interesting. I felt that my battery was going bad as it wouldn't really spining the starter when cold so I went to Costco and bought a new Red Top Optima. Put it in and she seemed ok for a few minutes then voltage dropped to 12V and later to 10.5 running. I figured that my 3G 130 amp alternator was toast so ordered a 170 amp 3G on EBay. Put it on and it charged for a few minutes and then back to 12V again.
Just for kicks I swapped the stock battery out of my daughter's Toyota for the Optima and after running for a few minutes she started charging again. Also the Optima is working fine in the Toyota. There must be something weird about our charging systems that it just wouldn't work with the Optima. Also I have been running an Optima Yellow Top in the trunk with a relay for my stereo for the last two years and had no problems. SonySC@hotmail.com

mm yet another update I readjusted the throttle, correctly ( I THINK) this time and adjusted the air bleed screw this time, and all is well......... all the problems seem to have been fixed.. until 2morrow when I realize I only made it worse