Low idle alt light on.

[bbob203]

I've got my idle down lower than I have ever had it about 750 rpm and to my surprise it's very quite and smooth almost no vibration not sure what this means but I dig it. Anyhow at calm idle no load on alt the cluster light is dimly lit and somewhat flickery but if I turn on the heater to high or the lights it goes off or if I artificially raise it by pressing my foot on the pedal and giving it a bit of go to bring it to 1000 rpm. I lowered my idle inadvertently when I turned down my max fuel screw tonite to see if I can't raise my fuel economy and clean up my smokey exhaust. Expecting to have to raise it back up I realized how nice it was idling and left it alone. Thoughts?

[vanbcguy]

Sounds about normal! It probably won't cause you any issues unless you are idling for hours at a time.

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[8v-of-fury]

When the idle is down and the light is on, check the charging voltage. I have seen this before. Interested to see if the voltage is down when the light is on or not.

[CRSMP5]

normal... step on brakes/put any load on charging system and will go out..

[ORCoaster]

Mine does that all the time after a fairly long run and charged battery.  If you can stand it at night, while waiting for a light to change leave it alone.  I need to bump my idle up from where you are now or I have trouble getting started on steep hills.  Like the one I live on.  Down only. 

[bajacalal]

Raise your idle. There's no reason for it to be that low.

Your fuel savings will be negligible but your alternator won't charge, your oil pressure will be lower and your water pump won't circulate coolant as efficiently, so it actually might run hot.

[bbob203]

hmm thanks gentlemen. Its so dang quite though like I'm not even driving a diesel. this was occuring after some hard fast cruising through the city so the battery was good and juiced up.

[vanbcguy]

hmm thanks gentlemen. Its so dang quite though like I'm not even driving a diesel. this was occuring after some hard fast cruising through the city so the battery was good and juiced up.

The alt light is flickering because the alt is just baaarely putting out enough juice to equal the battery voltage.  That light comes on when the battery voltage is greater than the alternator voltage (like when the alternator is non-functional for instance).  So a fully charged battery will actually make it flicker more than a low one.

If you really like your idle there and the light really causes you concern, you could always try finding a smaller alternator pulley.  Some of the factory alternator pulleys are actually adjustable - you can add a washer in the middle to spread the two halves further apart resulting in a smaller effective pulley size.  How much adjustment is available depends on where you are at now though.  If you have a tach it'll mess with the accuracy a bit too.

[CRSMP5]

10w lightbulb...... all it needs is something to use power... brake lights = 2 bulbs.. makes it go out... some type of voltage load...

why my gas car no do this... ahhh fuel pump/coil...

[bbob203]

I actually do have a solid  pulley on the bench vs the split one on the car was wondering wich one was better to run..

[8v-of-fury]

So on our diesels, its a poor mans "battery is charged" light ahha

[nwcali6]

  I like the sound of my diesel..clickity clack sounds like money in my bank account versus the gas guzzling gassers..

  I agree about the low idle and oil pressure, but if its your thing...

[Rising]

Mine used to do this as my alternator was on its way out. It would do it only at stop lights and such and only dimly. And then eventually it stopped charging my battery completely and died.

The new 90 amp I swapped in has no signs of that at all. Light comes on in the morning and goes out after first rev. Never to return.

Just my personal experience but mine didn't have anything to do with the idle speed...

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[CRSMP5]

ok.. if applying the brakes does not turn it off.. yes the alt is going bad or the fusebox is wet.. but hitting brakes/applying any load makes it go off.. its normal..