Hey guys, hoping to get some advice or find out if its a common problem.

Have a new alternator on my car. Replaced it about a year ago. The alternator is the only accesory on that belt I believe. Now it charges while driving (when fully charged it sticks around 13) however when idling in drive at a stop light it drops down to 9 or so depending on which accessories are on like lights or ac. When in park it rises to 13 for about 3 minutes until it drops again.

I do have a brand new interstate battery. This may be common but just gets me unnecessarily worried in traffic.

Thanks!

 

Don't rely on the dash board gauge, get a volt meter and check it in your driveway...probably drops when the fan kicks on as well...but check it with a meter.

It should get back to 14 volts or so, in a second or two.

 

Also check the alternator pigtail for any looseness. I had that happen once and I felt like an *** after 3 cs-144 alternators. Live and learn

 

Well, I come in a close second, replaced my first Alt cause of the gauge reading...mercy...2nd one the same thing

 

Haha. I was driving on the highway to work during hurricane sandy at the time and I notices the voltage drop to 9volts. Hahaha. Pulled the alternator at work and ran to Napa to get another. Drove for a week and it happened again, swapped again and noticed the connector was loose and it would drop til I pushed the connector. Felt like an idiot being a 12 year mechanic.. now I condemn connectors before components.

 

Went to AZ and took a good voltmeter read 12.8-13 in idle in park. With headlights, heat and radio on with car in drive drops below 12 to about 10.

Checked the alternator connection and it was on there solid and all the way. The idle does drop low about 400 in drive with those accessories on. Will have my ALT tested tommorow. Should be good though lol. Then again parts are just getting cheaper and cheaper.

 

That is kinda low. How are your grounds? I gained .75 volt back in a truck at work today just from a grungy ground.

 

Idle should come bqack up...I think the Alt is okay, just not spinning enough...did the volts come up with the engine speed higher?

 

Hey Mike,

Yes when you rev the engine the lights get brighter and it raises the voltage a bit

 

I think you have another issue that should be resolved first. The idle should come back to "normal" as if no accessories were on, within about a second or so.

 

It has a new IAC. What are some culprits?

 

Is there any way to raise the idle? Warm in park it sits about 600 but in drive bounce about 500rpm

 

Seems as if the IAC is not functioning properly...not that it is at fault, could be what the ECM see, etc.

I'd look into getting a scan tool to watch the IAC counts.

 

Would a volt meter help? I will go ahead and raise the idle today a little because it is really low. However I just noticed today that last night I accidently left the charger for a phone in the 12v. Drove it this morning and when it finally warmed up at idle it was charging even when stopped for a while. Maybe the voltage regulator? Because it was finally charging when the battery was drained

 

Volt meter won't help you, IIRC the IAC reads in stepper motor counts for position....not sure where or how you could tap in anywhere to monitor a voltage, nor what you would be seeing.

One question though, did you do the "reset min air" thing when you replaced the IAC?

Did you pull the TB and take it apart and clean all the passages?

FWIW, I bought my car new and replaced several hings over time, but have never had to touch the idle screw.

 

I did set the IAC when I got it. Don't recall a minimum air setting however.

Also when the water pump was replaced I took it apart and cleaned it out good