2002 Tahoe e-fans and volt gauge

88lance said:

Seen several posts about volt gauge bouncing around, but my situation seems a bit different since I just changed to electric fans, which is when it started.

So, '02 Z71 Tahoe, volt gauge always sits at 14 and never seems to move. I added electric fans and got rid of the clutch fan, and now when the fans kick on, the volt gauge bounces between 13-15 volts very quickly while the fans are on. When the fans clicks off, it stops at 14 and sits steady again.

At night you can actually see the fluctuations in the headlights and dash lights.

I have read that the alternator going bad is usually the cause for this, but since there was nothing wrong with the alternator before I added the fans, it makes me think it has something more to do with the fans causing the fluctuations, rather than something coincidentally going out right when I added the fans.

Anyone know what causes this?

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justirv said:

Take a look at your RPO codes in the glovebox. I believe the '02's with fan clutch came with a 105 amp alternator. When they transitioned to e-fans in '05, the alternator got bumped up to 130 amp. This could explain the voltage drop or "instability ". Can I ask what e-fan harness you used, is it '05 OEM or 3rd party (like Nelson, etc.). I ask to see how you connected the AC fan on command, by tapping into the AC clutch signal, or adding a pin for ECU control?

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Fless said:

Yours is KG8 so 130A, unless it's been changed. It's usually engraved into the housing on an OE alternator.

K68 = 105a
KG3 = 145a
KG8 = 130a

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Marky Dissod said:

Your alternator is a KG8 = 130A.
Next time you go to buy an alternator, LIE.
Tell them you have a KG3 or KG4, so you'll get a stronger alternator.
I upgraded to a KG3, and will not settle for a KG8 again.
Next time I'll try for a KG4.

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88lance said:

Could this fix the voltage fluctuation issue?
Is the KG4 higher amp than the KG3, or just better in other ways but still 145A?

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Marky Dissod said:

Two part answer.
Part 1. KG8 = 130A
KG3 = 140A
KG4 = 150A

If the alternator's connector, connects to the new alternator, you're good to go.

2. Every GM vehicle I've ever owned got a pcm tune.
One of the MANY things I get addressed, is turning up the idle from ≈500RpM, to about 600RPM.
In and of itself, that kept even my KG8 alternator from dozing off - but I upgraded anyway.

Also note I did the electrical fans upgrade. Also note your next mods in my sig.

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