voltage not even

[macdodd127]

I just replaced the engine in my '69 C10. Before putting the new engine in, we put on all the pulleys and also a newer alternator. All run off of a serpentine belt now. Question is, with the newer alternator, it surges back and forth at 12 to 14 volts at idle or in gear. Once the engine is revved up, the voltage is consistent at 14 volts. I'm wondering if the voltage regulator needs to be updated to one that is matched to the higher amperes of newer alternator? Of course, with the head lights on at idle or in gear, you can see the surge,,brighter/dimmer. Thanks Bill

[GASoline71]

Using an older non-internally regulated alternator? Or one of the newer "late model" alternators that are internally regulated so it will work with the serpentine?

If the alternator is internally regulated, you need to bypass the old voltage regulator mounted on the radiator support.

Gary

[davepl]

One-wire alternator? Might not be excited until you rev it up. If it's a three-wire, ignore me.

[macdodd127]

The alternator had two wires,,,,the newer one has a four prong male plug. We got a 4 prong female plug and wired to charge. The system seems to be charging ok,,just fluctuates at idle or in gear at idle. I've got a voltage gauge and it shows 14 volts when driving. Never shows discharging.

[macdodd127]

Well,,,I bypassed the voltage regulator,,,working good,,,14volts, everything works.