Alternator delays charging sometimes

[EL SHO]

ok guys, here's another mistery from my SHO, this time electrical (well the previous one was also electrical )

here's what happens.

Sometimes when I start the car the alternator delays charging the battery, it will take from less than one minute to all the way to 5 minutes to charge.
I installed an analog voltmeter below the radio just because of this and to know if my alternator is charging or not.

Whenever I move the key to the ON position and the battery light does NOT light up, I know the alternator will take some time to begin charging.

When the battery light on the dash lights up when the key is moved to the ON position, the alternator will begin chargin right away.

My battery is good, is a new Optima red top, my alternator is less than a year old and I took it to AutoZone to have it tested, it came out ok, diodes and voltage regulator.

So what could be the issue here? I've done some reading and some say that some alternators will need to "excite" before charging and some say that if the battery indicator light is bad it will also prevent any charging until later on since is part of the "readyness" circuit.

What do you guys think??

 

[BFedoroff]

There should be a resistor in parallel with the warning light, so that even if the light burns out, the alternator will still function. It sounds to me like the "I" circuit has a loose or dirty connection somewhere, either at the ignition switch, the cluster, the connector on the LH fender apron, or at the alternator. I would look at the connector on the LH fender apron first.

 

[hawkeye18]

A few things:

1) The battery indicator circuit is completely unrelated to charging. It's a simple differential circuit; the alternator provides output voltage to one side of it, and the battery provides voltage to the other side. If the battery light doesn't come on when you turn the key to ON, either a) the bulb's burnt out, or b) one of the wires broke. Either way, it doesn't affect your alternator one bit. The sense circuit (the one that tells the alt how much voltage the battery is generating, and therefore how much voltage the alternator needs to produce) is isolated from the dummy light circuit.

2) Just because Autozone tested the alternator and said it was good, that doesn't mean a damn thing. At least 75% of Autozone/Advance Auto employees have no clue whatsoever as to how to properly use that machine. I know this because my wife used to work at one, and the stories she'd tell me...

3) If the alternator won't charge for "a period of time", see if it'll start charging once the engine revs over about 3,000RPM. If it suddenly starts charging once you cross that threshold (or thereabouts), one of the diodes is bad. Every time.

Source: 10 years of electrical and electronics training and experience in the military

 

[SHOBlu]

Just because Autozone tested the alternator and said it was good, that doesn't mean a damn thing. At least 75% of Autozone/Advance Auto employees have no clue whatsoever as to how to properly use that machine. I know this because my wife used to work at one, and the stories she'd tell me...

AZ counterperson: "What kind of car?"

Customer: "Blue."

AZ counterperson: "Model?"

Customer: "Oh..... Dodge."

:laugh_ti::laugh_ti::laugh_ti::laugh_ti:

 

[SHOZ123]

Could be the brushes hanging up if it is not rpm related.

 

[EL SHO]

Thanks for all the advice guys.

What I've done to try to solve this issue so far is to beef up the ground terminals, a friend and I installed 3 more ground terminals, we also found that the middle ground wire (I believe since it's color black) at the alternator harness is cut, only half of the copper wires are left and the green wire is sliced open but the copper wires are still intact. We also fixed that.

So far it has been charging and the new ground terminals seemed to help a lot to lower the resistance. We did a test with the car running, all accesories on and the engine revving at 2k, we placed the positive terminal from the voltmeter to the negative side battery post and the negative voltmeter terminal to the alternator housing and before we installed all the new ground terminals the resistance was high, it was showing .06 and after the new terminals/wires is not at .01

Also, just in case we took the old alternator to a shop to have it tested first and then rebuilt with a new voltage regulator. All diodes tested fine and the regulator was replaced with a brand new one. So now I have a spare Alt in case the current Alt in the car has a fried diode and goes down.