Power problem

ranger952 · September 4, 2004

Hi all,

I have a 98 Silverado, 1/2 ton. Recently, I have replaced the battery, alternator, and most of the battery cables, with the exception of the long one that runs to the driver side power center.

I still have a power drop to 12 volts on the guage when I run the lights or AC.

Any idea on what to check? I am going to check the ground that goes to the frame next to the battery tomm. I know the one that runs to the block is good.

Matt99Z71 · September 4, 2004

If you turn those two off does it jump back to 14 volts?

budhayes3 · September 4, 2004

Could have a bad or corroded ground somewhere or possibly a junk alternator. Is the alternator new or reman? I've personally had bad luck with reman electrical parts. (alternator,wiper motor)

Or you could drive around at night with the lights and ac off...nothin like sweatin in the dark while driving...pretty safe

GMC_MTR_4X4 · September 4, 2004

it could also be your voltage regulator.

ranger952 · September 4, 2004

It does go back to 14 volts if those things are off.

Where is the voltage regulater? I thought it was inside the alternator.

budhayes3 · September 4, 2004

It does go back to 14 volts if those things are off.
Where is the voltage regulater? I thought it was inside the alternator.

You are correct, it's inside the alternator.

tryn2lrn · September 4, 2004

Is it a high output altenator? I believe most do this at low rpms when well loaded. High outputs alts are worse at low rpms.

ranger952 · September 5, 2004

Nope. It's a stock type alternator.

ranger952 · September 5, 2004

One problem might be the size of the alt.

Anyone know if this truck should have the 105 or 120 amp alt? No one seems to know which one is takes.....

kdm101 · September 5, 2004

One problem might be the size of the alt.
Anyone know if this truck should have the 105 or 120 amp alt? No one seems to know which one is takes.....

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Check your RPO codes. Here's the list from the '98 list posted elsewhere on this board:

KG9 Generator, 140 Amp

KW2 Generator, 124 Amp

KXB Dual Generator, 100 Amp

K60 Generator: 100 Ampere

K68 Generator: 105 Ampere